Expandable trans-septal sheath

ABSTRACT

Disclosed is an expandable transluminal sheath, for introduction into the body while in a first, low cross-sectional area configuration, and subsequent expansion of at least a part of the distal end of the sheath to a second, enlarged cross-sectional configuration. The sheath is configured for use in the vascular system and has utility in the performance of procedures in the left atrium. The access route is through the inferior vena cava to the right atrium, where a trans-septal puncture, followed by advancement of the catheter is completed. The distal end of the sheath is maintained in the first, low cross-sectional configuration during advancement to the right atrium and through the atrial septum into the left atrium. The distal end of the sheath is subsequently expanded using a radial dilatation device. In an exemplary application, the sheath is utilized to provide access for a diagnostic or therapeutic procedure such as electrophysiological mapping of the heart, radio-frequency ablation of left atrial tissue, placement of left atrial implants, mitral valve repair, or the like.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of U.S. ProvisionalApplication 60/871,091 filed Dec. 20, 2006, the entire contents of whichare hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to medical devices for percutaneously accessingbody lumens and cavities and, more particularly, to methods and devicesfor accessing the cardiovascular system.

2. Description of the Related Art

A wide variety of diagnostic or therapeutic procedures involves theintroduction of a device into the vasculature through a percutaneousincision at an access site. Such regions of the vasculature, preferredfor access, include both the arteries and veins, typically at peripherallocations in the body. Typical access sites include the jugular vein,the subclavian artery, the subclavian vein, the brachial artery andvein, the femoral arteries and the femoral veins. Techniques commonlyknown for such vascular access include the Seldinger technique. TheSeldinger technique involves using a hollow needle to puncture the skinand gain access to the selected artery or vein. A guidewire is nextplaced through the hollow needle into the selected region ofvasculature. The guidewire may be advanced to a target location in thevasculature, often more than 100 cm away from the access site. Theneedle is removed and a tapered dilator with a sheath and a centrallumen in the dilator is advanced over the guidewire into thevasculature. The dilator is next removed and a guide catheter isadvanced through the sheath over the guidewire. The guide catheter canbe advanced all the way, or part way, to the target site. The guidecatheter, following or without removal of the guidewire, can be used fordirecting therapeutic or diagnostic catheters to regions of thevasculature and central circulation, including external and internalstructures of the heart. A general objective of access systems, whichhave been developed for this purpose, is to minimize the cross-sectionalarea of the access lumen, while maximizing the available space for thediagnostic or therapeutic catheter placement therethrough. Theseprocedures are especially suited for coronary angioplasty, stentplacement, cerebrovascular coil placement, prosthetic heart valvereplacement, diagnostic cardiac catheterization, and the like.

Electrophysiology (EP) mapping and cardiac tissue ablation proceduresare examples of diagnostic or therapeutic interventional procedures thatare commonly performed on the heart. The procedure involves the steps ofinserting a hollow needle into the femoral vein via a percutaneouspuncture. A guidewire is next inserted through the central lumen of theneedle into the femoral vein. The guidewire is routed, underfluoroscopic control, cranially toward the heart until it reaches theright atrium via the inferior vena cava. The hollow needle is removedand a sheath with a tapered tip central obturator further including acentral guidewire lumen, termed a dilator, is routed over the guidewire,through the skin puncture, through the wall of the femoral vein, andinto the central lumen of the femoral vein. The central obturator ordilator is next removed. A Mullins catheter is next routed through thesheath, over the guidewire, and advanced to the right atrium. Theguidewire is removed and a Brockenbrough™ (Trademark of C.R. Bard,Inc.)-type needle is inserted through the proximal end of the Mullins™catheter and routed to the right atrium. The Mullins catheter ispositioned, under fluoroscopic guidance, so that its distal end islocated in the Foramenal valley, a feature in the septal wall ofmyocardium that divides the right atrium from the left atrium. TheForamenal valley is the remains of a communication between the right andleft atrium, which exists prior to birth, but which closes followingbirth due to the pressures imposed by the beating heart of the newborninfant. The Brockenbrough needle is next advanced through the atrialseptum in the general region of the Foramenal valley. The Mullinscatheter is next advanced over the Brockenbrough needle until its distalend resides within the left atrium. Hemostatic valves at the proximalend of all hollow devices permit sealing around catheters and devicesinserted therethrough with corresponding prevention or minimization ofblood loss and the entry of air.

The procedure continues with the Brockenbrough needle being withdrawnand replaced with a 0.032 to 0.038 inch diameter guidewire, generally ofthe stiff variety. This guidewire may have a bifurcated distal end toprevent inadvertent retraction once the guidewire has been advanced andexpanded into the left atrium. The Mullins catheter is next withdrawnand replaced with a guide catheter having internal dimensions generallyaround 8 French and a tapered, removable obturator. The guide catheteris advanced into the right atrium and across the atrial septum,following which the obturator is removed. At this time, diagnostic andtherapeutic catheters can be advanced into the left atrium so thatappropriate EP mapping and ablation can occur. However, problemssometime arise, when trying to pass the guide catheter across the atrialseptum, in that the tract generated by the Brockenbrough needle andMullins catheter closes too tightly to allow passage of the guidecatheter. At this point, a balloon catheter is advanced over theguidewire and through the guide catheter. The balloon catheter isadvanced so that its dilatation balloon traverses the atrial septum. Theballoon catheter is next inflated to stretch the tissues surrounding theatrial septal puncture. At this time, the guide catheter can have itsdilator re-inserted and the entire assembly advanced over the guidewirethrough the atrial septum and into the left atrium.

Current therapeutic techniques may involve advancing an EP mappingcatheter through the guide catheter and positioning the EP mappingcatheter at various locations within the left atrium. Electrocardiogramsignals are sensed by the EP mapping catheter. These signals areconducted or transmitted from the distal tip to the proximal end overelectrical lines routed along the length of the EP catheter. The signalsare analyzed by equipment electrically connected to the proximal end ofthe EP mapping catheter. Catheter guidance is generally accomplishedusing X-ray fluoroscopy, ultrasound imaging such as ICE, TEE, and thelike. Therapy generally involves radio-frequency (RF) electromagneticwave generation by external equipment electrically connected to an EPtherapeutic catheter. The EP therapeutic catheter is advanced into theleft atrium into regions of foci of electrical interference of thehearts normal electrical conduction. Application of such radio-frequencyenergy at the tip of the EP therapeutic catheter, which is brought intocontact with the myocardium, causes tissue ablation and the eliminationof the sources of these spurious signals or re-entry waveforms. Aprimary area targeted for RF tissue ablation is the area surrounding theorigin of the pulmonary veins. Often a ring-type electrode is beneficialin performing this procedure. Such tissue ablation can be performedusing RF energy to generate heat, but it can also be performed usingmicrowaves, Ohmic heating, high-intensity focused ultrasound (HIFU), oreven cryogenic cooling. The cryogenic cooling may have certainadvantages relative to heating methodologies in that tissue damage islessened. Although a single atrial septal puncture may be adequate forelectrophysiological mapping of the left atrium, therapeutic systems,including RF ablation devices often require that two atrial septalpunctures be performed. A risk of atrial septal punctures includespotentially perforating the aorta, a high-pressure outlet line, whichresides quite close to the atrial septum.

Provision is generally made to deflect instrumentation throughsubstantial angles, between 20 and 90 degrees, within the right atriumto gain access to the atrial septum from a catheter routed craniallywithin the inferior vena cava. To address this situation, theBrockenbrough needle, the Mullins catheter, or both devices, aresubstantially curved devices. Significant skill is required, on the partof the cardiologist or electrophysiologist to negotiate the path to theatrial septum and into the left atrium using a Brockenbrough needle anda Mullins catheter.

One of the primary issues that arise during electrophysiology proceduresin the heart is the need to remove and replace multiple instrumentsmultiple times, which is highly expensive and adds substantial time tothe conduct of the procedure. A reduction in the number of catheter andguidewire passes and interchanges would reduce procedure time, reducethe risk of complications, improve patient outcomes, reduce proceduralcost, and increase the number of cases that could be performed at agiven catheterization lab. Current procedures involving multiple atrialseptal penetrations would be reduced in frequency or become less timeconsuming and less risky if only a single atrial septal penetration wasnecessary. Additional benefit could be derived if larger catheters couldbe used, thus enabling the use of more sophisticated, powerful, andaccurate instruments to improve patient outcomes. The limitations ofcurrent systems are accepted by physicians but the need for improvedinstrumentation is clear. Furthermore, placement of implants within theleft atrium, such as the Atritech Watchman™ or the Microvena PLAATO™would be facilitated if a larger working channel could be madeavailable.

Further reading related to the diagnosis and treatment of atrialfibrillation (AF) includes Hocini, M, et al., Techniques for CurativeTreatment of Atrial Fibrillation, J. Cardiovasc Electrophysiol, 15(12):1467-1471, 2004 and Pappone, C and Santinelli, V, The Who, What, Why,and How-to Guide for Circumferential Pulmonary Vein Ablation, J.Cardiovasc Electrophysiol, 15(10): 1226-1230, 2004. Further reading onRF ablation includes Chandrakantan, A, and Greenberg, M, RadiofrequencyCatheter Ablation, eMedicine, topic 2957 Oct. 28, 2004. Further readingregarding catheter approaches to treating pathologies of the left atriuminclude Ross, et al, Transseptal Left Atrial Puncture; New Technique forthe Measurement of Left Atrial Pressure in Man, Am J. Cardiol, 653-655,May 1959 and Changsheng M, et al., Transseptal Approach, anIndispensable Complement to Retrograde Aortic Approach forRadiofrequency Catheter Ablation of Left-Sided Accessory Pathways, J. HKColl Cardiol, 3:107-111,1995.

A need, therefore, remains for improved access technology, which allowsa device to be percutaneously or surgically introduced, endovascularlyadvanced to the right atrium, and enabled to cross the atrial septum byway of a myocardial puncture and Dotter-style follow-through. The devicewould further permit dilation of the myocardial puncture in the regionof the atrial septum so that the sheath could pass relatively largediameter instruments or catheters, or multiple catheters through thesame puncture. Such large dilations of the tissues of the atrial septumneed to be performed in such a way that the residual defect is minimizedwhen the device is removed. It would be beneficial if a cardiologist orhospital did not need to inventory and use a range of catheterdiameters. It would be far more useful if one catheter or introducersheath diameter could fit the majority of patients or devices. Ideally,the catheter or sheath would be able to enter a vessel or body lumenwith a diameter of 3 to 12 French or smaller, and be able to passinstruments through a central lumen that is 14 to 30 French. The sheathor catheter would be capable of gently dilating the atrial septum usingradially outwardly directed force and of permitting the exchange ofinstrumentation therethrough without being removed from the body. Thesheath or catheter would also be maximally visible under fluoroscopy andwould be relatively inexpensive to manufacture. The sheath or catheterwould be kink resistant, provide a stable or stiff platform for atrialseptum penetration, and minimize abrasion and damage to instrumentationbeing passed therethrough. The sheath or catheter would further minimizethe potential for injury to body lumen or cavity walls or surroundingstructures. The sheath or catheter would further possess certainsteering capabilities so that it could be negotiated through substantialcurves or tortuosity and permit instrument movement within the sheath.

SUMMARY OF THE INVENTION

A transluminal, radially expanding access sheath is provided accordingto an embodiment of the present invention. In an embodiment, theradially expanding access sheath is used to provide access to the leftatrium by way of a trans-septal puncture and advancement in the atrialseptum dividing the right and left atriums. In an embodiment, the sheathcan have an introduction outside diameter that ranges from 3 to 12French with a preferred range of 5 to 10 French. The diameter of thesheath can be expandable to permit instruments ranging up to 30 Frenchto pass therethrough, with a preferred range of between 3 and 20 French.The sheath can have a working length ranging between 40-cm and 200-cmwith a preferred length of 75-cm to 150-cm. The ability to pass thetraditional electrophysiology therapeutic and diagnostic catheters andinstruments as well as larger, more innovative, instruments through acatheter introduced with a small outside diameter is derived from theability to atraumatically expand the distal end of the catheter orsheath to create a larger through lumen to access the cardiac chambers.The ability to pass multiple catheters through a single sheath with asingle septal penetration is inherently safer and less time-consumingthan a multiple septal puncture procedure. The expandable distal end ofthe catheter can comprise between 5% and 95% of the overall workinglength of the catheter. The proximal end of the catheter is generallylarger than the distal end to provide for pushability, torqueaqbility(preferably approximately 1:1 torqueability), steerability, control, andthe ability to easily pass large diameter instruments therethrough. Inan embodiment, the sheath can be routed to its destination over one ormore already placed guidewires with a diameter ranging from 0.010 inchesup to 0.040 inches and generally approximating 0.035 to 0.038 inches indiameter. An advantage of approaching the treatment site by the veins,instead of the arteries, is that the venous pressure is lower than thatin the arterial system, thus reducing the potential for catastrophichemorrhage during the procedure. Another advantage of the system is thatthe sheath and dilator assembly are flexible enough to track over aguidewire and be steered by either the guidewire or by a Brockenbroughneedle, inserted through the central lumen of the dilator.

One embodiment of the invention comprises an endovascular access systemfor providing minimally invasive access to atrial structures of themammalian heart. The system includes an access sheath comprising anaxially elongate tubular body that defines a lumen extending from theproximal end to the distal end of the sheath. At least a portion of thedistal end of the elongate tubular body is radially expandable from afirst, smaller cross-sectional profile to a second, greatercross-sectional profile. In an embodiment, the first, smallercross-sectional profile is created by making axially oriented folds inthe sheath material. These folds may be located in only onecircumferential position on the sheath, or there may be a plurality ofsuch folds or longitudinally oriented crimps in the sheath. The folds orcrimps may be made permanent or semi-permanent by heat-setting thestructure, once folded. In an embodiment, a releasable or expandablejacket is carried by the access sheath to restrain at least a portion ofthe elongate tubular structure in the first, smaller cross-sectionalprofile during insertion and up to or during inflation of the distalregion. In another embodiment, the jacket is removed prior to insertingthe sheath into the patient. In an embodiment, the elongate tubular bodyis sufficiently pliable to allow the passage of objects having a maximumcross-sectional size larger than an inner diameter of the elongatetubular body in the second, greater cross-sectional profile. Theadaptability to objects of larger dimension is accomplished bypliability or re-shaping of the cross-section to the larger dimension inone direction accompanied by a reduction in dimension in a lateraldirection. The adaptability may also be generated through the use ofmalleable or elastomerically deformable sheath material. This re-shapingor non-round cross-section can be beneficial in passing two or morecatheters through a single sheath with a minimum lateral cross-sectionalarea. In one embodiment, the sheath tube comprises a reinforcing layerembedded within a membrane layer fabricated from polymeric materials. Inone embodiment, an inner and outer layer of the sheath tube arefabricated from different polymers. In one embodiment, length of thesheath is between 50 and 250 cm. In one embodiment, the inner lumen ofthe sheath ranges between 6 and 30 French when the distal region isfully expanded.

In another embodiment of the invention, a transluminal access sheathassembly for providing minimally invasive access comprises an elongatetubular member having a proximal end and a distal end and defining aworking inner lumen. In this embodiment, the tubular member comprises afolded or creased sheath that can be expanded by a dilatation balloon.The dilatation balloon, if filled with fluids, preferably liquids andfurther preferably radiopaque liquids, at appropriate pressure, cangenerate the force to radially dilate or expand the sheath. Thedilatation balloon is removable to permit subsequent instrument passagethrough the sheath. Longitudinal runners may be disposed within thesheath to serve as tracks for instrumentation, which further minimizefriction while minimizing the risk of catching the instrument on theexpandable plastic tubular member. Such longitudinal runners arepreferably circumferentially affixed within the sheath so as not toshift out of alignment. In yet another embodiment, the longitudinalrunners may be replaced by longitudinally oriented ridges and valleys,termed flutes. The flutes, or runners, can be oriented along thelongitudinal axis of the sheath, or they can be oriented in a spiral, orrifled, fashion.

In each of the embodiments, the proximal end of the access assembly,apparatus, or device is preferably fabricated as a structure that isflexible, resistant to kinking, and further retains both column strengthand torqueability. Such structures include tubes fabricated with coilsor braided reinforcements and preferably comprise inner walls thatprevent the reinforcing structures from protruding, poking through, orbecoming exposed to the inner lumen of the access apparatus. Suchproximal end configurations may be single lumen, or multi-lumen designs,with a main lumen suitable for instrument, guidewire, endoscope, orobturator passage and additional lumens being suitable for control andoperational functions such as balloon inflation. Such proximal tubeassemblies can be affixed to the proximal end of the distal expandablesegments described heretofore. In an embodiment, the proximal end of thecatheter includes an inner layer of thin polymeric material, an outerlayer of polymeric material, and a central region comprising a coil,braid, stent, plurality of hoops, or other reinforcement. It isbeneficial to create a bond between the outer and inner layers at aplurality of points, most preferably at the interstices or perforationsin the reinforcement structure, which is generally fenestrated. Suchbonding between the inner and outer layers causes a braided structure tolock in place. In another embodiment, the inner and outer layers are notfused or bonded together in at least some, or all, places. When similarmaterials are used for the inner and outer layers, the sheath structurecan advantageously be fabricated by fusing of the inner and outer layerto create a uniform, non-layered structure surrounding thereinforcement. The polymeric materials used for the outer wall of thejacket are preferably elastomeric to maximize flexibility of thecatheter. The polymeric materials used in the composite catheter innerwall may be the same materials as those used for the outer wall, or theymay be different. In another embodiment, a composite tubular structurecan be co-extruded by extruding a polymeric compound with a stent,braid, or coil structure embedded therein. The reinforcing structure ispreferably fabricated from annealed metals, such as fully annealedstainless steel, titanium, or the like. In this embodiment, onceexpanded, the folds or crimps can be held open by the reinforcementstructure embedded within the sheath, wherein the reinforcementstructure is malleable but retains sufficient force to overcome anyforces imparted by the sheath tubing.

In an embodiment of the invention, it is beneficial that the sheathcomprise a radiopaque marker or markers. The radiopaque markers may beaffixed to the non-expandable portion or they may be affixed to theexpandable portion. Markers affixed to the radially expandable portionpreferably do not restrain the sheath or catheter from radial expansionor collapse. Markers affixed to the non-expandable portion, such as thecatheter shaft of a balloon dilator can be simple rings that are notradially expandable. Radiopaque markers include shapes fabricated frommalleable material such as gold, platinum, tantalum, platinum iridium,and the like. Radiopacity can also be increased by vapor depositioncoating or plating metal parts of the catheter with metals or alloys ofgold, platinum, tantalum, platinum-iridium, and the like. Expandablemarkers may be fabricated as undulated or wavy rings, bendable wirewound circumferentially around the sheath, or other structures such asare found commonly on stents, grafts, stent-grafts, or catheters usedfor endovascular access in the body. Expandable radiopaque structuresmay also include disconnected or incomplete surround shapes affixed tothe surface of a sleeve or other expandable shape. Non-expandablestructures include circular rings or other structures that completelysurround the catheter circumferentially and are strong enough to resistexpansion. In another embodiment, the polymeric materials of thecatheter or sheath may be loaded with radiopaque filler materials suchas, but not limited to, bismuth salts, or barium salts, or the like, atpercentages ranging from 1% to 50% by weight in order to increaseradiopacity. The radiopaque markers allow the sheath to be guided andmonitored using fluoroscopy.

In order to enable radial or circumferential expansive translation ofthe reinforcement, it may be beneficial not to completely bond the innerand outer layers together, thus allowing for some motion of thereinforcement in translation as well as the normal circumferentialexpansion. Regions of non-bonding may be created by selective bondingbetween the two layers or by creating non-bonding regions using a sliplayer fabricated from polymers, ceramics or metals. Radial expansioncapabilities are important because the proximal end needs to transitionto the distal expansive end and, to minimize manufacturing costs, thesame catheter may be employed at both the proximal and distal end, withthe expansive distal end undergoing secondary operations to permitradial or diametric expansion.

In another embodiment, the distal end of the catheter is fabricatedusing an inner tubular layer, which is thin and lubricious. This innerlayer is fabricated from materials such as, but not limited to, FEP,PTFE, polyamide, polyethylene, polypropylene, Pebax, Hytrel, and thelike. The reinforcement layer comprises a coil, braid, stent, orplurality of expandable, foldable, or collapsible rings, which aregenerally malleable and maintain their shape once deformed. Preferredmaterials for fabricating the reinforcement layer include but are notlimited to, stainless steel, tantalum, gold, platinum, platinum-iridium,titanium, nitinol, and the like. The materials are preferably fullyannealed or, in the case of nitinol, fully martensitic. The outer layeris fabricated from materials such as, but not limited to, FEP, PTFE,polyamide, polyethylene, polypropylene, polyurethane, Pebax, Hytrel, andthe like. The inner layer is fused or bonded to the outer layer throughholes in the reinforcement layer to create a composite unitarystructure. The structure is crimped radially inward to a reducedcross-sectional area. A balloon dilator is inserted into the structurebefore crimping or after an initial crimping and before a final sheathcrimping. The balloon dilator is capable of forced radial, or diametric,expansion of the reinforcement layer, which provides sufficient strengthnecessary to overcome any forces imparted by the polymeric tubing, thuscontrolling the cross-sectional shape of the polymeric tubing. Thedilator is also capable of overcoming any forces imparted by tissues,including atrial or even ventricular myocardial tissue, through whichthe sheath is inserted.

Another embodiment of the invention comprises a method of providingendovascular access to the left atrium. The method first comprisespercutaneously placing a hollow needle into the femoral vein, insertinga guidewire through the hollow needle into the vein, withdrawing theneedle, and inserting a sheath with a tapered obturator into thepuncture site and into the vein over the guidewire. The guidewire isnext withdrawn, as is the tapered obturator and a 0.032 to 0.038-inchstiff guidewire is advanced into the vein and to the level of the rightatrium or superior vena cava (SVC) through the inferior vena cava (IVC).A radially expandable sheath is next advanced into the femoral vein andadvanced past the right atrium into the superior vena cava over theguidewire. The guidewire is next withdrawn and replaced with aBrockenbrough-type needle, which is advanced through the guidewire lumenof the expandable sheath. The Brockenbrough needle comprises a curved orbent distal end that can be used as a steering mechanism for theexpandable sheath. The expandable sheath, with Brockenbrough needleinserted therethrough, is withdrawn caudally, turned toward the medialdirection, and the distal tip is positioned against the Foramen Ovale ofthe atrial septum with the Brockenbrough needle withdrawn just insidethe tip of a sheath dilator, which is pre-inserted within the radiallycollapsed sheath. The Brockenbrough-type needle is advanced through theatrial septum into the left atrium while maintaining the expandablesheath in position against the septal wall, either by normal cardiacmovement or by mechanical forward force on the Brockenbrough needle. Theexpandable sheath is next advanced axially through the septal wall, overthe Brockenbrough-type needle and the needle, affixed to its controlwire is withdrawn from the proximal end of the expandable sheath. Thedilator, positioned within the expandable sheath is next radiallyexpanded causing the distal end of the sheath to expand radially so asto dilate the hole in the tissues of the atrial septum. The dilator is,next, deflated and removed form the sheath, leaving a large centrallumen for the passage of instruments into the left atrium. The expandedsheath is capable of holding a single instrument or multiple instrumentsof, for example, 8 to 10 French diameter. Suitable hemostatic andanti-reflux valves and seals are affixed the distal end of all devicesexcept guidewires to ensure maintenance of hemostasis and prevention ofair entry into the vasculature. Following therapeutic or diagnosticprocedures, or both, the sheath is withdrawn from the patient allowingthe septal puncture to close, thus preventing communication of bloodbetween the right and left atrium.

The expandable access sheath is configured to bend, or flex, aroundsharp corners and be advanced into the right atrium so that thelongitudinal axis of its distal end is perpendicular to the atrialseptal wall. Provision can optionally be made to actively orient orsteer the sheath through the appropriate angles of between 20 to 120degrees or more and to bend in one or even two planes of motion. Thesteering mechanism, in various embodiments, can be a curved guidewireand straight catheter, curved catheter and straight guidewire, a movablecore guidewire, or a combination of the aforementioned. The expandablesheath also needs to be able to approach the right atrium from a varietyof positions. In one embodiment, radial expansion of the distal end ofthe access sheath from a first smaller diameter cross-section to asecond larger diameter cross-section is next performed, using a balloondilator. The balloon dilator is subsequently removed from the sheath topermit passage of instruments that may not normally have been able to beinserted into the atrium of the heart. Once the sheath is in place, theguidewire may be removed or, preferably, it may be left in place. Theatrial septum is gently dilated with radial force, preferably to adiameter of 10 mm or less, rather than being axially or translationallydilated by a tapered dilator or obturator. In most embodiments, the useof the expandable trans-septal sheath eliminates the need for multipleaccess system components.

In another embodiment of the invention, the expandable sheath comprisessteerable members that eliminate the need for a 0.038-inch guidewire tobe placed prior to sheath insertion and advancement. In anotherembodiment, the Brockenbrough-type needle, or septal penetrator, isintegrated into the expandable sheath so that it can be used to puncturethe atrium but does not need to be advanced and withdrawn through thesheath. The integral septal penetrator is actuated by the operator atthe proximal end of the sheath. The controls at the proximal end of thesheath are operably connected to the septal penetrator at the distal endof the sheath by linkages, pressure lumens, electrical lines, or thelike, embedded within the sheath and routed from the proximal end to thedistal end. The septal penetrator is capable of bending with thearticulating sheath distal region. In yet another embodiment, areversible fixation device, or safety cushion, is provided at the distalend of the expandable sheath. The reversible fixation device is actuatedby the operator at the proximal end of the sheath. The controls at theproximal end of the sheath are operably connected to the fixation deviceat the distal end of the sheath by linkages, pressure lumens, electricallines, or the like, embedded within the sheath and routed from theproximal end to the distal end. The reversible fixation device can be aninflatable structure such as a balloon, a moly-bolt expandablestructure, an expandable mesh, an umbrella, or the like, preferablypositioned to expand within the left atrium. In an embodiment, thestructure of the catheter or sheath is such that it is able to maintaina selectively rigid operating structure sufficient to provide stabilityagainst the atrial septum to support the advancement of trans-septalneedles or penetrators. The sheath can be selectively stiffened, atleast at its distal end, to provide a non-deflecting platform forsupport of instrumentation, such as the septal penetrator, which ispassed therethrough.

In another embodiment of the invention, the proximal end of theexpandable sheath comprises hemostasis or backflow check seals or valvesto prevent blood loss and retrograde flow of air into the circulatorysystem. The hub of the sheath comprises such hemostasis seal. The sealcomprises an annular soft elastomeric gasket that seals againstcatheters, instruments, and the dilator, inserted therethrough. The sealcan further comprise a valve such as a stopcock, one-way valve such as aduckbill or flap valve, or the like to prevent significant blood lossand air entry when an instrument or catheter is removed from the lumenof the expandable sheath. The soft annular seal can further comprise amechanism to compress the inner diameter of the seal radially inward,such as the mechanisms found on Tuohy-Borst valves. The hub furthercomprises one or more sideport for injection of contrast media such asOmnipaque, Renografin, or other Barium-loaded solutions, for example, oranticoagulant solutions such as heparin, coumadin, persantin, or thelike, or for the measurement of pressure at or near the distal end ofthe sheath. The dilator hub comprises a central lumen with a Tuohy-Borstvalve and one or more sideports for balloon inflation, said sideportsoperably connected to lumens in the dilator catheter for injection orwithdrawal of fluids from a balloon at the distal end of the dilator andoptionally for measurement of pressure at or near the dilator distalend. The dilator hub can also comprise a slide knob, a trigger, or otherlever to actuate a septal puncture device at the distal end of thedilator. The dilator hub, the sheath hub, or both, can also comprise ahandle, lever, or trigger mechanism to enable steering mechanisms at thedistal end of the dilator, the sheath, or both, respectively.

The expandable sheath, in an embodiment, comprises radiopaque markers todenote the beginning and end of the expandable region, and the middle ofthe expandable region. The middle of the expandable region is useful inthat it can be aligned with the atrial septum during the sheathexpansion procedure. The sheath can comprise radiopaque materials suchas gold wire, platinum wire, tantalum wire, or coatings of theaforementioned over a malleable, stainless steel, deformable reinforcinglayer. Such complete radiopaque markings are especially useful forsheath dilation insofar as they allow the operator to more clearlyvisualize the extent to which the sheath has been dilated once thedilator is activated. In a preferred embodiment, a radiopaque markerband is affixed to the dilator substantially near the distal tip of thedilator so that the position of the distal tip can be observed andcontrolled relative to the wall of the left atrium or other cardiacstructures. This radiopaque marker band can be a non-expandable, axiallyelongate tubular structure that is adhered to the non-expandable dilatorshaft. Another non-expandable radiopaque marker band can be adhered tothe dilator shaft at a position substantially corresponding to theproximal most dilating portion of the dilator or sheath. Anothernon-expandable radiopaque marker band can be adhered to the dilatorshaft at a position substantially corresponding to the distal mostdilating portion of the dilator or sheath. Thus, the atrial septum canbe positioned with confidence between the two dilator radiopaque markersand dilation will be assured. The radiopaque marker bands can further beconfigured to appear different under fluoroscopy, for example by makingthe distal tip marker a single band, the distal dilation marker twobands, and the proximal dilator marker, three bands. Yet anotherconfiguration of radiopaque marker bands can be achieved by usingmalleable wire windings of gold, tantalum, platinum alloys, or the like,which are embedded within the folded and expandable sheath, preferablyat or near the distal end of the sheath and, optionally, at or near theproximal end of the expandable portion of the sheath. These wirewindings can expand with the sheath and can help show the extents of thesheath even after the dilator has been removed.

Since the hub of a Trans-Septal sheath requires many hemostasis valvesand fluid input connectors or ports, the hub can be a longer structurethan that on current guide catheters. Therefore, it may be required thata longer Brockenbrough needle is used to allow sufficient working lengthto provide for maneuverability within the cardiac anatomy. It can bebeneficial to use Brockenbrough needles, which are longer than thestandard 60-71 cm length, preferably those of 85 to 95 cm in length.Furthermore, the sheath hub length can be advantageously foreshortenedby use of tightly grouped ports and minimum length Tuohy-Borst valves aswell as “Y” connectors that are integrated into the hub, rather thanbeing separately attached. Thus, the working length of the entire systemis between 50 and 90 cm and preferably between 60 and 80 cm. In anexemplary embodiment, the working length of the entire system is 70 to73 cm. The sheath hub length, including the length of the dilator hub,can range between 3 and 15 cm and preferably between 4 and 8 cm, thepreferred length being appropriate if a shorter 70-cm or 71-cm longBrockenbrough needle is used.

In order to facilitate maneuvering the expandable trans-septal sheathinto the right atrium and through the atrial septum, as well as forsupport of the sheath during catheter passage therethrough, it isbeneficial to impart a curve into the trans-septal sheath, andoptionally through the dilator. This curve is preferably a bend ofbetween 20 to 120 degrees and preferably between 30 and 90 degrees. Thebend can be in one plane or it can be in two orthogonal planes. Anexemplary bend is to bend the sheath approximately 45 degrees out ofplane 1 and approximately 50 degrees out of line in plane 2, which isorthogonal to plane 1. The radius of the curve can range between 2-cmand 12-cm and preferably between 3-cm and 10-cm in each of the twodirections. Another example is a single plane curve of 90 degrees with aradius of around 3-cm to 12-cm. These bends are preferably imparted tothe distal region of the non-expandable sheath tubing, just proximal tothe expandable region. The bends can also be imparted through theexpandable region but maintaining those bends in the expandable regionmay further require the use of a bent or curved shaped balloon, aresilient longitudinal support within the expandable region, a bent orcurved dilator shaft, or both. The bending can be imparted to the tubingby placing the tubing over a curved mandrel and then heat-setting thetubing while over the mandrel. The tubing needs to be heated aboveglass-transition temperature, which is preferably above body temperature(37 degrees centigrade) for the heat set to be optimal. Materials usedin the heat settable region can include, but not be limited to,polyethylene, PEN, PET, polyamide, polyimide, PEBAX, Hytrel, and thelike. The expandable region of a trans-septal sheath need not be longand ranges between 0.5-cm and 20-cm with a preferred length of between1-cm and 10-cm. By keeping the expandable region short, the region ofthe sheath comprising the bend, which allows the sheath have propertiessimilar to those of a guiding catheter, is not in the expandable region,but rather just proximal to the expandable region. In other embodiments,methodologies of maintaining a bend within the expandable region aredisclosed herein.

In yet another embodiment, the exterior of the sheath, and optionallythe internal lumen of the sheath, can be coated with a lubriciouscoating comprising materials such as, but not limited to, silicone oilor a hydrophilic hydrogel comprising polyethylene glycol, polyetherpolyurethane, or the like. Other coatings can include antimicrobialcoatings such as those fabricated from silver azide or anticoagulantcoatings such as those comprising heparin.

In another embodiment, the proximal end of the sheath comprises anon-circular interior cross-section. The interior cross-section of thesheath can be oval, or it can comprise two or more completely walled offor partially walled off separate lumens. The sheath hub, which isaffixed to the non-expandable proximal end of the sheath, can comprisetwo or more separate instrumentation ports, each of which are operablyconnected to a lumen or partial lumen within the sheath and which canadvantageously comprise hemostasis valves. The instrumentation ports areespecially useful for passage of, for example, multipleelectrophysiology catheters, a mapping catheter and a therapeuticcatheter, a ring catheter and an ablation catheter, or the like.Segregation of the multiple instruments can be useful to prevent bindingor interference between the multiple catheters or instruments passedthrough the sheath. In yet another embodiment, the proximal end of thesheath has a non-circular cross-section that minimizes the overallcross-sectional area or circumference of a sheath configured to accepttwo or more catheters. This non-circular cross-section can be an oval,ellipse, rounded triangle, or the like. The non-circular cross sectioncan, for example, reduce an 18 French OD catheter to around 15.5 French,using the same wall thickness and still retain the capability to accepttwo 8 French catheters within its internal lumen or lumens. Reduction inexterior cross-section is clearly useful in making the procedure asminimally invasive as possible and may make a procedure, which normallytakes a cutdown, a percutaneous procedure.

In another embodiment, the guidewire port on the dilator hub is operablyconnected to a sideport. The sideport further comprises a flexible lineand a luer connector and may further comprise an optional stopcock,needle valve, or a one way valve. The sideport can be a T-fitting,Y-fitting, or it can be integrally molded with the guidewire port on thedilator hub. The guidewire port can be preferably terminated at itsproximal end with a hemostasis valve, a Tuohy-Borst fitting, or othervalve or seal system.

For purposes of summarizing the invention, certain aspects, advantagesand novel features of the invention are described herein. It is to beunderstood that not necessarily all such advantages may be achieved inaccordance with any particular embodiment of the invention. Thus, forexample, those skilled in the art will recognize that the invention maybe embodied or carried out in a manner that achieves one advantage orgroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein. These and other objectsand advantages of the present invention will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A general architecture that implements the various features of theinvention will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrateembodiments of the invention and not to limit the scope of theinvention. Throughout the drawings, reference numbers are re-used toindicate correspondence between referenced elements.

FIG. 1 is a front view schematic representation of the human venouscirculatory system including the heart and the great veins;

FIG. 2 is a front view schematic representation of the human venouscirculatory system with a guidewire routed from the femoral vein intothe right atrium;

FIG. 3 is a front view schematic representation of the human venouscirculatory system with an expandable sheath advanced into the rightatrium, according to an embodiment of the invention;

FIG. 4 is a cross-sectional illustration of the heart with theexpandable sheath articulated and positioned within the right atrium andthe guidewire removed, according to an embodiment of the invention;

FIG. 5 is a cross-sectional illustration of the heart with theexpandable sheath positioned at the atrial septum and the septalpenetrator advanced across the atrial septum into the left atrium,according to an embodiment of the invention;

FIG. 6 is a cross-sectional illustration of the heart with theexpandable sheath advanced into the left atrium across the atrial septumand the septal penetrator withdrawn into the dilator of the expandablesheath, according to an embodiment of the invention;

FIG. 7 is a cross-sectional illustration of the heart with theexpandable sheath dilated at its distal end by the dilator, according toan embodiment of the invention;

FIG. 8 is a cross-sectional illustration of the heart with theexpandable dilator withdrawn from the sheath leaving a large centrallumen for instrument passage into the left atrium, according to anembodiment of the invention;

FIG. 9 is a cross-sectional illustration of the heart with anelectrophysiology therapeutic catheter advanced through the centrallumen of the expanded sheath into the left atrium, according to anembodiment of the invention;

FIG. 10 is a cross-sectional illustration of the heart with an atrialseptal plug delivery catheter advanced through the central lumen of theexpanded sheath into the left atrium, according to an embodiment of theinvention;

FIG. 11 is a cross-sectional illustration of the heart with acollapsible mitral valve prosthesis delivery catheter advanced throughthe central lumen of the expanded sheath into the left atrium, accordingto an embodiment of the invention;

FIG. 12 is a cross-sectional illustration of the heart with theexpandable sheath traversing into the left atrium and secured in placewith a left atrial anchor system, according to an embodiment of theinvention;

FIG. 13 is a cross-sectional illustration of the expandable sheathshowing the proximal sheath and dilator hubs along with varioushemostasis valves, actuators, and seals, according to an embodiment ofthe invention;

FIG. 14 is a cross-sectional illustration of the expandable sheathshowing a deflection mechanism, according to an embodiment of theinvention;

FIG. 15 is a cross-sectional illustration of the expandable sheathshowing a distal anchor mechanism, according to an embodiment of theinvention;

FIG. 16 is a cross-sectional illustration of the expandable sheathshowing an atrial septal penetrator integral to the dilator, accordingto an embodiment of the invention;

FIG. 17A illustrates a side view of a collapsed, non-expandedtrans-septal sheath, according to an embodiment of the invention;

FIG. 17B illustrates a side view of an expanded trans-septal sheath,according to an embodiment of the invention;

FIG. 17C illustrates a side view of an expanded trans-septal sheath withthe dilator removed, according to an embodiment of the invention;

FIG. 18A illustrates a lateral cross-section of the proximal region ofthe expandable trans-septal sheath, according to an embodiment of theinvention;

FIG. 18B illustrates a lateral cross-section of the distal region of theexpandable trans-septal sheath in its non-expanded configuration,according to an embodiment of the invention;

FIG. 19 illustrates a side view of a trans-septal sheath comprisingmultiple instrumentation ports on its hub, according to an embodiment ofthe invention;

FIG. 20A illustrates a side view of the distal end of a trans-septalsheath and dilator comprising curvature near its distal end tofacilitate trans-septal puncture, according to an embodiment of theinvention;

FIG. 20B illustrates a side view of the distal end of a trans-septalsheath and dilator in partial cross section showing the distal taperedfairing and its relationship to the folded expandable distal region ofthe sheath, according to an embodiment of the invention;

FIG. 21A illustrates a side view of a hemostasis adapter configured toserve as a plug for a large central lumen of a sheath hub, according toan embodiment of the invention;

FIG. 21B illustrates the hemostasis adapter of FIG. 21A inserted intothe central Tuohy-Borst valve of a sheath hub, according to anembodiment of the invention;

FIG. 22A illustrates a distal end of an expanded trans-septal sheathwith the dilator removed, showing the malleable reinforcement structure,according to an embodiment of the invention; and

FIG. 22B illustrates a distal end of an expanded trans-septal sheathwith the dilator removed, showing the malleable reinforcement structureand a parallel wound radiopaque coil, according to an embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. The described embodimentsare to be considered in all respects only as illustrative and notrestrictive. The scope of the invention is therefore indicated by theappended claims rather than the foregoing description. All changes thatcome within the meaning and range of equivalency of the claims are to beembraced within their scope.

In the description below, reference will be made to a catheter or asheath, which can be an axially elongate hollow tubular structure havinga proximal end and a distal end. The axially elongate structure furthercan have a longitudinal axis and has an internal through lumen thatextends from the proximal end to the distal end for the passage ofinstruments, fluids, tissue, or other materials. The axially elongatehollow tubular structure can be generally flexible and capable ofbending, to a greater or lesser degree, through one or more arcs in oneor more directions perpendicular to the main longitudinal axis. Thetubular structure generally has a generally circular cross-section butin other embodiments can have oval, rectangular or other cross-sectionalshape. As is commonly used in the art of medical devices, the proximalend of the device is that end that is closest to the user, typically acardiologist, surgeon, or electrophysiologist. The distal end of thedevice is that end closest to the patient or that is first inserted intothe patient. A direction being described as being proximal to a certainlandmark will be closer to the user, along the longitudinal axis, andfurther from the patient than the specified landmark. The diameter of acatheter is often measured in “French Size” which can be defined as 3times the diameter in millimeters (mm). For example, a 15 Frenchcatheter is 5 mm in diameter. The French size is designed to approximatethe circumference of the catheter, in millimeters, and is often usefulfor catheters that have non-circular cross-sectional configurations.While the original measurement of “French” used π (3.14159 . . . ) asthe conversion factor between diameters in millimeters (mm) and French,the system has evolved today to where the conversion factor is 3.0.

FIG. 1 is a schematic frontal (anterior) illustration (lookingposteriorly) of a human patient 100 comprising a heart 102, a descendingaorta 104, an inferior vena cava 106, a superior vena cava 108, a rightjugular vein 110, a left jugular vein 112, a subclavian vein 114, aright femoral vein 116 and a left femoral vein 118. In thisillustration, the left anatomical side of the body of the patient 100 istoward the right of the illustration. FIG. 1 primarily illustratescomponents of the venous circulation.

Referring to FIG. 1, the heart 102 is a pump, the outlet of which is theaorta, including the descending aorta 104, which is a primary artery inthe systemic circulation. The circulatory system, which is connected tothe heart 102 further comprises the return, or venous, circulation. Thevenous circulation comprises the superior vena cava 108 and the inferiorvena cava 106, which return blood from the upper extremities and lowerextremities, respectively. The right and left jugular veins, 110 and112, respectively, and the subclavian vein 114 are smaller venousvessels with venous blood returning to the superior vena cava 108. Theright and left femoral veins, 116 and 118 respectively, return bloodfrom the legs to the inferior vena cava 106. The veins carry blood fromthe tissues of the body back to the right heart, which then pumps theblood through the lungs and back into the left heart. Pressures withinthe venous circulation generally average 20 mm Hg or less. The arteriesof the circulatory system carry oxygenated blood (not shown) from leftventricle of the heart 102 to the tissues of the body. The pressureswithin the arteries for a normal person undulate, with a modifiedtriangle waveform, between a diastolic pressure of around 80 mm Hg to asystolic pressure of around 120 mm Hg. A hypotensive person may havearterial pressure lower than 120/80 mm Hg and a hypertensive person mayhave arterial pressures higher than 120/80 mm Hg. Systolic arterialpressures of 300 mm Hg can occur in extremely hypertensive persons.

FIG. 2 is a schematic frontal illustration, looking posteriorly from theanterior side, of the patient 100. A vascular introduction sheath 204has been inserted into the right femoral vein 116 via a percutaneouspuncture or incision. A guidewire 200 has been inserted through theintroduction sheath 204 and routed, cranially, up the inferior vena cava106 to the right atrium 202, one of the chambers of the heart 102. Inthis illustration, the left anatomical side of the patient 100 is towardthe right. The guidewire 200 has been placed so that it can be used totrack therapeutic or diagnostic catheters into a region of the heart102.

Referring to FIG. 2, The venous circulation, through which the guidewire200 has been routed, is generally at lower pressure between 0 and 20 mmHg than is the systemic circulation, of which the descending aorta is apart. The pressure within the systemic circulation may range from 60 toover 300 mm Hg depending on the level of hypertension or hypotensionexistent in the patient. By accessing the heart through the venouscirculation, the chance of hemorrhage from the catheter insertion siteis minimized, as is the demand on the hemostasis valves built into anycatheters used on the patient.

FIG. 3 is a frontal illustration, looking posteriorly from the anteriorside, of the patient 100. The vascular introduction sheath 204 of FIG. 2has been removed from the right femoral vein 116 and a largerTrans-Septal Expandable Sheath 300 has been inserted into the venouscirculation over the guidewire 200 and routed through the inferior venacava 106 into the right atrium 202 of the heart 102. The expandabletrans-septal sheath 300 further comprises a dilator 306, the proximalmost part of which is shown in FIG. 3. The expandable trans-septalsheath 300 further comprises a proximal non-expandable region 304 and adistal expandable region 302.

Referring to FIG. 3, the venous circulation is filled with blood (notshown) that is somewhat depleted of oxygen and enriched with carbondioxide as a result of interaction with body tissues. In the illustratedembodiment, the expandable region 302 of the expandable trans-septalsheath 300 is smaller in diameter than the proximal non-expandableregion 304.

FIG. 4 is a cross-sectional illustration of the heart 102, furthercomprising the descending aorta 104, the inferior vena cava 106, thesuperior vena cava 108, the right atrium 202, a right ventricle 400, aleft ventricle 402, a left atrium 404, and a left atrial appendage 406.The heart 102 also comprises an aortic arch 408, a ventricular septum410, a mitral valve 412, an aortic valve 414, a pulmonary valve 416, atricuspid valve 418, and a pulmonary artery 420. The expandable region302 of the sheath 300 is visible in the right atrium 202 and theproximal non-expandable region 304 of the expandable trans-septal sheath300 is visible in the inferior vena cava 106.

Referring to FIG. 4, the expandable distal region 302 has beenarticulated or deflected in an arc so that its distal end rests againstthe atrial septum (not shown), the wall of myocardium that divides theright atrium from the left atrium. In this illustration, the atrialseptum is obscured by the ascending aorta 602 (FIG. 6), that region ofaorta between the aortic arch 408 and the aortic valve 414, as well asthe pulmonary artery 420 and the pulmonary valve 416. The distal end ofthe distal sheath region 302 is positioned so that it rests within theForamenal valley of the atrial septum, a naturally thin area of theatrial septum and a preferred landmark for continuing the procedure. Thedistal region 302 can be articulated, in an embodiment, with the use ofan integral or removable internal steering mechanism. The distal region302, in another embodiment, can be articulated using a movable coreguidewire or a bent guidewire (not shown) inserted through the centrallumen of the distal region 302 of the sheath 300.

FIG. 5 is a cross-sectional illustration of the heart 102, showing theatrial septum 504. The ascending aorta 602 (FIG. 6), aortic valve 414,pulmonary artery 420, and pulmonary valve 416 of FIG. 4 have beenremoved from this illustration for clarity and to show the atrial septum504. The distal expandable region 302 of the sheath 300, substantiallylocated within the right atrium 202, is shown with its long axisperpendicular to the atrial septum 504. The proximal end 304 of thesheath 300 is shown resident within the inferior vena cava 106. A septalpenetrator 500 is shown extended through a puncture 502 in the atrialseptum 504 and is routed into the left atrium 404. The distal expandableregion 302 further comprises the foldable distal radiopaque marker 506and the proximal radiopaque marker 508.

Referring to FIG. 5, the septal penetrator 500 is a needle or axiallyelongate structure with a sharp, pointed distal end. The septalpenetrator 500 can be resident within the guidewire lumen of the dilator306 (FIG. 3), which can be removably resident within the distalexpandable region 302. The septal penetrator 500 can be actuated at theproximal end of the sheath 300. The septal penetrator 500 can beoperably connected to a control mechanism such as a button, lever,handle, trigger, etc., which can be affixed, permanently or removably,at the proximal end of the dilator 306 by way of a linkage, pusher rod,electrical bus, or the like that runs the length of the dilator 306. Thepenetrator 500 can also be integrated into the sheath 300 but theremovable dilator 306 can be more advantageous. Care must be taken notto have the septal penetrator 500 pierce the wall of the left atrium 404opposite the atrial septum 504 so length control and advance control areimportant as can be guidance, either by fluoroscopy, MRI, ultrasound, orthe like. Further care must be taken not to inadvertently pierce theaorta in the region upstream or anatomically proximal to the aortic arch408 (FIG. 4). The distal expandable region 302 can be bent, deflected,or articulated through an angle of between 30 and 120 degrees to achieveapproximate perpendicularity with the atrial septum 504. The septalpenetrator 500 can be solid, it may be hollow like a hypodermic needle,or it may have a “U” or “C”-shaped cross-section. The center or core ofa hollow, “C”, or “U”-shaped septal penetrator can be filled with aguidewire or other core element to prevent incorrect tissue penetration.The septal penetrator 500 can be rigid or it can be flexible but retaincolumn strength. Such flexible configurations can comprise cutouts inthe wall of the penetrator 500 or guidewire-like construction. Theseptal penetrator 500 can be initially straight or it can be initiallycurved. The septal penetrator 500 can be fabricated from shape memorymaterial such as nitinol and heat treated to cause curving once thematerial is heated from martensitic to austenitic temperatures. Suchheating can be performed using electrical heating, hot water injection,or the like. Preferred temperatures for the austenite finishtemperature, in this application range from 25 degrees to around 42degrees centigrade. Higher temperatures require more heating and rely onhysteresis to minimize the return to the martensite phase when theheating temperature is removed. The distal foldable radiopaque marker506 and the proximal foldable radiopaque marker 508 can be fabricated aseither flat or round wire from metals such as, but not limited to, gold,platinum, iridium, titanium, tantalum, and the like. The distal foldableradiopaque marker 506 can be advantageously located near the distal endof the foldable section 302 while the proximal foldable radiopaquemarker 508 can be advantageously located 1 to 10 cm, and preferably 2 to4 cm proximal to the distal foldable marker 506. The foldable radiopaquemarkers 506 and 508 are malleable and embedded within the wall of thefoldable section 302 and can be deformed and folded with a linear creaseto minimize their diameters to facilitate delivery of the sheath 300.

FIG. 6 illustrates a cross-sectional view of the heart 102 showing thedistal expandable region 302 having been advanced across the atrialseptum 504 from the right atrium 202 and into the left atrium 404. Thetapered tip 600 of the dilator 306 leads the distal end of theexpandable region 302 through the septal puncture 502 created by thepenetrator 500. That region of the ascending aorta 602 that does notobscure this anterior view of the atrial septum 504 is shown. Theproximal non-expandable region 304 has advanced, to follow the advancingdistal expandable region 302, so that the proximal region 304 can belocated not only in the inferior vena cava 106 but also within the rightatrium 202. The distal expandable region 302 further comprises theproximal foldable radiopaque marker 508 and the distal foldableradiopaque marker 506. The markers 506 and 508 are shown in theirradially collapsed, folded configuration.

Referring to FIG. 6, the expandable access sheath 300 can bepre-assembled with its internal dilator 306. The dilator 306 can be, inan embodiment, a catheter with a dilatation balloon (not shown) affixedto a dilator shaft. The dilatation balloon can be preferably anangioplasty-type, non-elastomeric balloon and can be fabricated frommaterials such as, but not limited to, PET, polyamide, cross-linkedpolyolefins, or the like. The dilator shaft can be terminated at itsproximal end with an inflation port that can be operably connected to alumen within the dilator shaft. The lumen within the dilator shaft canbe operably connected to the interior of the balloon by way of scythesor other openings. The tapered tip 600 can be affixed to the distal endof the dilator 306 and can be fabricated from Hytrel, a thermoplasticelastomer such as C-Flex, or from elastic polymers such as siliconeelastomer, polyurethane, or the like. The tapered tip 600 can have ageneral funnel shape tapering from small at the distal end to large atthe proximal end. In another embodiment, the tapered dilator tip 600 canhave a complex taper with two or more angles and can also includeintermediate cylindrical, non-tapered, regions. The tapered tip 600 canbe made to expand with the distal end of the balloon and then shrinkdown with the balloon when it is deflated, facilitating withdraw throughthe lumen of the expanded distal region 302 of the sheath 300. Thetapered tip 600 can be asymmetric to substantially match thecross-sectional configuration of an expandable sheath section that canbe folded and has inherently axial asymmetry. The foldable radiopaquemarkers 506 and 508 are visible under fluoroscopy or X-ray visualizationand can be used to guide the sheath 300 across the atrial septum 504.The distal foldable radiopaque marker 506 can be configured to belocated within the left atrium and across the atrial septum 504 when itis correctly located in its target position prior to expansion. Theproximal foldable radiopaque marker 508 can be configured to be locatedwithin the right atrium and proximal to the atrial septum 504 such thatthe markers approximately evenly straddle the atrial septum 504. Theatrial septum 504 can be visualized as a dark spot on fluoroscopy if itis painted with radiopaque contrast media injected through the centrallumen of the Brockenbrough needle (not shown).

FIG. 7 illustrates a cross-sectional view of the heart 102 showing thedistal expandable region 302 having been radially expanded while placedacross the atrial septum 504 between the right atrium 202 and the leftatrium 404. The distal expandable region 302 is now generally of thesame diameter as the proximal region 304. The distal expandable region302 further comprises the proximal foldable radiopaque marker 508 andthe distal foldable radiopaque marker 506. The markers 506 and 508 areshown in their radially expanded, full diameter configuration. Thedistal foldable radiopaque marker 506 and the proximal foldableradiopaque marker 508 are shown correctly positioned and substantiallyequidistant on opposite sides of the atrial septum 504. The transitionzone 700 can be that region connecting the distal region 302 and theproximal region 304. The dilator balloon resides within the transitionzone 700 as well as the distal expandable region 302. The puncture 502in the atrial septum 504 has now been dilated using radial dilationmeans and the distal end of the sheath 302 can be resident within theleft atrium 404. The dilator tip 600 remains within the left atrium 404.The use of radial dilation can be considered beneficial and superior totranslation dilation by tapered axially translating dilators with regardto tissue healing and wound closure. The radial dilation allows theseptal transit to be performed with relatively small expandable tips inthe range of 7 to 10 French. Following transit of the septum through theperforation created by the penetrator, a small sheath with a smooth,tapered, distal transition can be advanced readily through thepenetration. The expandable region 302 can then be dilated radially,opening up the septal penetration to any size from 12 to 30 French. Suchradially, or circumferentially, dilated openings are known to heal morecompletely, following removal of the instrument. In another embodiment,the expandable region 302 can be expanded by forcing an inner dilator(not shown) distally along the long axis of the sheath 300 to force theexpandable region 302 to dilate diametrically. Such axial translationdilation can be generated by way of a pusher affixed to the innerdilator at its distal end and a handle or mechanical lever at theproximal end of the sheath 300. The expandable region 302 can beelastomeric or comprise one or more longitudinal folds, which cause thecircumference, and thereby the diameter, to be small until dilated.

FIG. 8 illustrates a cross-sectional view of the heart 102 wherein thedistal end of the distal expandable region 302 can be resident withinthe left atrium 404 and can be located across the atrial septum 504. Thetip 600 (FIGS. 6 and 7) of the dilator 306 (not shown) has been removedand withdrawn from the proximal end of the sheath 300. In thisconfiguration, the sheath 300 retains a large, central lumen capable ofpassing instrumentation, catheters, or the like into the left atrium404. The size of the sheath 300 can be substantially the same whether inthe distal expandable region 302 or the proximal non-expandable region304. The central lumen of the sheath can be exposed to pressure withinthe left atrium 404, said left atrial pressures being 20 mm Hg or less.This large sheath 300 can be capable of delivering one, two, or morecatheters into the left atrium 404 without the need for more than oneatrial septal puncture 502. The distal expandable region 302 furthercomprises the proximal foldable radiopaque marker 508 and the distalfoldable radiopaque marker 506. The markers 506 and 508 are shown intheir radially expanded, unfolded configuration and the sheath 300 iscorrectly positioned across the atrial septum 504 to provide catheteraccess to the left atrium through the sheath 300. In another embodiment,only a distal foldable marker 506 can be comprised by the sheath 300,while in yet another embodiment, only a proximal foldable radiopaquemarker 508 can be comprised by the sheath.

FIG. 9 illustrates a cross-sectional view of the heart 102 wherein thedistal end of the distal expandable region 302 can be resident withinthe left atrium 404 and can be located across the atrial septum 504. Twoof the outlets for the pulmonary veins 902 are shown within the leftatrium 404. The tissue around the pulmonary veins 902 is often a sitefor re-entrant waveforms that cause atrial arrhythmias. Ablation of thistissue using heat or extreme cold temperatures (cryogenics) canalleviate the arrhythmias. In the illustrated embodiment, an electrode904 that emits Radiofrequency (RF) energy has been introduced at the endof an electrophysiology catheter 900 into the right atrium 404 throughthe expandable sheath 300. The electrode 904 shown can be a roundelectrode called a lasso electrode and can be capable of heating andablating a ring of tissue in a single operation. Single point electrodes904 can create line or ring ablations but must be drawn slowly along thetissue to ablate the desired pattern. Such electrode movement can bedifficult to achieve at the end of a curved 100-cm long, or longer,catheter being monitored by fluoroscopy or ultrasound. The heatingelectrodes can deliver energies such as microwaves, radio frequencies,high-intensity focused ultrasound (HIFU), and the like. Because thesering electrodes 904 are large in diameter, they may be advantageouslyplaced through very large sheaths such as the expandable trans-septalsheath 300.

FIG. 10 illustrates a cross-sectional view of the heart 102 wherein thedistal end of the distal expandable region 302 of the expandabletrans-septal sheath 300 can be resident within the left atrium 404 andcan be located across the atrial septum 504. A delivery catheter 1000for an implantable device 1002 can be routed through the expandablesheath 300. In this embodiment, the implantable device 1002 can be anexpandable plug capable of closing off the opening between the leftatrium 404 and the left atrial appendage 406. The implantable device1002 can be releasably affixed to the distal end of the catheter 1000 bya releasable coupler 1004, activated by a linkage extending between thedistal coupler 1004 and the proximal end of the delivery catheter 1000.Such left atrial appendage 406 plugs or filters have been shown toreduce emboli generation by the left atrial appendage 406 in conditionswhere the left atrium 404 is in a state of atrial fibrillation, oruncoordinated muscle contraction. Atrial fibrillation, while not lifethreatening, results in reduced cardiac output and exercise tolerance.It can be also associated with a high rate of cerebrovascular embolicstroke. Left atrial appendage implants 1002 are radially collapsibleduring delivery. They are generally delivered through 14 French orlarger catheters and a radially expandable delivery sheath would beadvantageous.

FIG. 11 illustrates a cross-sectional view of the heart 102 wherein thedistal end of the distal expandable region 302 of the expandabletrans-septal sheath 300 can be resident within the left atrium 404 andcan be located across the atrial septum 504. A mitral, or aortic, valveimplant delivery catheter 1100 can be routed through the expandablesheath 300. The catheter 1100 can be controllably, releasably, affixedto the inlet side of a collapsible, mitral valve prosthesis 1102 by acoupler 1104. The coupler 1104 can be operably connected to the proximalend of the delivery catheter 1100 by a linkage. The delivery catheter1100 can be required to articulate to reach the mitral valve orifice toplace the mitral valve prosthesis 1102. The mitral valve prosthesis 1102can be expanded so that it engages the remnants of the diseased mitralvalve leaflets 1106 so that it can be secured in place. Such aprosthesis can be necessarily large, (up to 35 mm diameter fullyexpanded) and requires a very large trans-septal catheter (20 to 30French), even for a radially collapsed device. The expandabletrans-septal catheter 300 would allow placement of such large deviceswith minimal damage to the atrial septum 504. Similar techniques can beused for placement of an aortic valve with access gained through afemoral, subclavian, or iliac artery.

FIG. 12 illustrates a cross-sectional view of the heart 102 wherein thedistal end of the distal expandable region 302 of the expandabletrans-septal sheath 300 can be resident within the left atrium 404 andcan be located across the atrial septum 504. A distal anchor 1200 isshown inflated within the left atrium 404 for the purpose of stabilizingthe sheath 300 so that its expandable region 302 cannot be inadvertentlypulled out of the left atrium 404. Two electrophysiology catheters 1202are shown extending into the left atrium 404 out the distal end of theexpandable region 302. An inflation lumen 1204 is illustrated riding onthe surface of the sheath 300 in both the proximal region 304 and thedistal expandable region 302. The inflation lumen 1204 can be operablyconnected to an inflation port and valve at the proximal end of thesheath 300 and can be operably connected to the interior of the distalanchor 1200. The distal anchor, in this embodiment, can be a balloon.The balloon can be either non-compliant like an angioplasty balloon orcompliant like a Foley balloon, the latter of which can be fabricatedfrom silicone elastomer, latex rubber, polyurethane, or the like.Non-compliant balloons can be made from cross-linked polyethylene orpolypropylene or from stretch blow molded polyethylene terephthalate,polyamides, or the like. In another embodiment, a second balloon 1506(FIG. 15) can be placed so that it expands within the right atrium 202against the atrial septum 504. Inflation of the second balloon 1506 canbe performed through the same inflation lumen 1204 as that used for thedistal anchor 1200. Such inflation through the same inflation lumen 1204would be substantially simultaneous with the distal anchor 1200.Inflation of any of the balloons can be performed using a high-pressureinflation device that is operably connected to an inflation lumen 1204.The high-pressure inflation device can be used to inject fluid such as,but not limited to, saline, contrast media, carbon dioxide, or the likeinto the balloon to generate the desired inflation and diameterincrease. The second balloon 1506 would prevent distal migration of thesheath 300. In another embodiment, a dumbbell shaped balloon wouldreplace the two separate balloons. The small diameter part of thedumbbell balloon can be configured to reside within the puncture site502. Such dumbbell balloon can be preferably fabricated as anon-compliant balloon. The distal anchor could also be fabricated as amoly-bolt, umbrella, expandable braid, or other expandable structureactivated by a linkage to the proximal end of the sheath. Fabrication ofthe distal anchor can be achieved using materials such as, but notlimited to, polyolefins such as polyethylene or polypropylene,polyamide, polyurethane, polyester, elastomeric materials, Hytrel,Pebax, or the like.

FIG. 13 illustrates a longitudinal cross-section of the proximal end1300 of an expandable trans-septal sheath system. The proximal end 1300comprises a dilator shaft 1302, a sheath shaft 1304, an anchor inflationline 1306, a fluid infusion line 1308, an anchor line stopcock 1310, afluid infusion valve 1312, a sheath hub 1314, a sheath valve 1316, adilator inflation port 1318, a dilator hub 1320, a dilation stopcock1322, a guidewire port valve 1324, a penetrator shaft 1326, a penetratorknob 1328, a penetrator spring (not shown), a penetrator access port1330, an anchor inflation lumen 1332, and a penetrator linkage 1334.

FIG. 14 illustrates a longitudinal cross-section of an articulatingexpandable trans-septal sheath 1400. The articulating, expandable sheath1400 further comprises a proximal region 1402, a distal expandableregion 1404, a sheath hub 1406, a transition zone 700, a central lumen1412, a steering linkage lumen 1424, an anchor inflation line 1306, afluid infusion line 1308, a compression cap 1414, a variable valveelement 1316, a lever support 1418, a steering lever 1420, a steeringlinkage 1422, and a steering linkage distal fixation point 1426. In thisembodiment, the articulation can be generated by tension or compressionforce in the steering linkage 1422 being applied to the fixation point1426 affixing the steering linkage 1422 to the distal end of the distalexpandable region 1404. The distal expandable region can be flexible andcan be made preferentially more flexible in the region just proximal tothe distal fixation point 1426. The lever 1418 provides mechanicaladvantage and can be used with ratchets, locks, friction elements, orthe like to restrict movement of the lever 1418 and consequently thelinkage 1422 when manual pressure is removed. The distal end of thesheath 1400 is shown bent, or articulated, into an arc and the lever1420 can be correspondingly moved forward, relative to the hub 1406, tocause tension in the linkage 1422. A second lever support 1418, steeringlever 1420, steering linkage 1422, distal fixation point 1426 andsteering linkage lumen 1424 can be added, in another embodiment, topermit articulation of the distal region 1404 in a second direction.

FIG. 15 illustrates a longitudinal cross-section of an articulatingexpandable sheath 1400 further comprising a distal anchor 1508, aproximal anchor 1506, and a plurality of anchor bonds 1510. The sheath1400 further comprises an anchor inflation lumen 1332, a plurality ofscythes 1504, an anchor inflation manifold 1502, an anchor inflationline 1306, an anchor inflation valve 1312, a hub 1406 and a centralsheath lumen 1412. The distal anchor 1508 and the proximal anchor 1506are shown as balloons that are inflated with fluid, preferably saline,water, or radiopaque contrast media. Inflation occurs through the anchorinflation valve 1312, the anchor inflation line 1306, the anchorinflation manifold 1502 within the hub 1406, and the anchor inflationlumen 1332, which are all operably connected. Fluid pressure is added orremoved to the balloons 1506 and 1508 through the scythes 1504, whichare holes or ports in the wall of the sheath 1400 that expose the regioninside the distal anchor 1508 and proximal anchor 1506 to the fluidpressure of the anchor inflation lumen 1332.

FIG. 16 illustrates a longitudinal cross-section of a dilator 1600suitable for use with an expandable trans-septal sheath 1400 (FIG. 15).The dilator 1600 further comprises a dilator hub 1320, a guidewire portwith valve 1324, a penetrator access port 1330, an optional penetratorshaft 1326, an optional penetrator knob 1328, a penetrator spring (notshown), an optional penetrator linkage 1334, an optional penetrator1302, an optional penetrator coupler 1606, an optional penetrator portclosure 1602, an inner dilator tube 1610, an outer dilator tube 1612, afiller tube 1628, further comprising an optional filler tube distal bond1630, a dilatation balloon 1604, a plurality of balloon bonds 1608, anda plurality of radiopaque markers 1620, 1622, 1624, 1626. The penetratorlinkage 1334 and the penetrator 1302 can be solid, coiled, hollow tubes,or C-shaped. The C-shaped embodiment can be capable of further acceptinga guidewire in the guidewire lumen 1614 at the same time as thepenetrator 1302 and penetrator linkage 1334. The spring (not shown) canbe located between the penetrator knob 1328 and the penetrator portclosure 1602 and allows the penetrator 1302 to be advanced temporarilyand then retracted to its safety position automatically. The guidewirecan serve the function of plugging a central hole or hollow within thepenetrator 1302. The penetrator 1302 can be a curved or a straightneedle, or it may be fabricated from shape memory materials such asnitinol and be configured to be inserted straight but bend upon exposureto Ohmic heating, body temperature, hot water flushed therethrough, orthe like. The dilator balloon 1604 can be preferably an angioplasty-typeunfurling balloon with bonds at its proximal and distal end. The balloon1604 can be fabricated from high-strength materials such as, but notlimited to, PET, polyamide, cross-linked polymers, polyethylene, and thelike. The balloon 1604 and dilator 1600 can be fabricated to generatepressures of up to about 20 atmospheres without leakage or failure.

Referring to FIG. 16, the radiopaque markers 1620, 1622, 1624, and 1626are all of the non-expandable type and are affixed to catheter orballoon tubing using adhesive, compression fit, interference fit,potting, over-molding, or the like. The radiopaque markers 1620, 1622,1624, and 1626 are fabricated as short, axially elongate hollowcylinders using materials such as, but not limited to, platinum, gold,tantalum, iridium, barium, bismuth, or the like. The distal tipradiopaque marker 1620 can be affixed over, or distal to, the balloonbond 1608 for ease of assembly and can be generally covered by a distalshroud or fairing (not shown). The radiopaque markers 1622, 1624 and1626 are affixed to the inner tubing 1610 prior to attachment of thedilator balloon 1604. The radiopaque marker 1622 delineates theapproximate distal end of the full diameter region of the dilatationballoon 1604. The radiopaque marker 1626 delineates the approximateproximal end of the full diameter region of the dilatation balloon 1604.The marker 1626 can also be positioned to correspond to the proximal endof the fully expandable portion of the sheath (not shown). The marker1624 can be generally optional and corresponds with the approximatecenter of the balloon 1604 or the expandable portion of the sheath (notshown). The inclusion of the radiopaque markers 1622, 1624, 1626facilitates fluoroscopic visualization of the expandable portion of thesheath (not shown) or the dilatation balloon 1604 across the atrialseptum to ensure correct positioning during sheath expansion. The distalmarker 1620 facilitates fluoroscopic visualization of the distal tip ofthe dilator 1600 to ensure that it does not impinge on, perforate, ordamage cardiac or other tissue structures within the body and that itfollows the desired path within the patient. The distal dilator ROmarker 1620 can be the most important of the RO markers in that it canbe used to guide Brockenbrough needle advance and retraction duringdeployment of the system. In an embodiment, the filler tube 1628 can beused to surround the outer dilator tube 1612 to fill the dead spacebetween the outer dilator tube 1612 and the inside of the sheath throughwhich the dilator 1600 can be inserted. In an embodiment, the fillertube 1628 can be welded or bonded to the outer dilator tube 1612 at thedistal filler bond 1630. The dilator sleeve, or filler tube 1628, can befabricated from the same materials, including Hytrel, PEBAX,polyurethane, PVC, and the like, as those used for the outer dilatortube 1612. The filler tube 1628 provides a sheath system that can bemore pushable and has increased resistance to kinking than would existif the filler tube 1628 were omitted and a greater annular distanceexisted between the dilator outer tube 1612 and the sheath tubing (notshown).

FIG. 17A illustrates a radially expandable sheath system 1700, shown inits radially compressed configuration, comprising a dilator 1600 and anexpandable trans-septal sheath 1400. The sheath 1400 further comprises aproximal anchor 1506, a distal anchor 1508, a sheath radiopaque marker1702, a chevron transition zone 1704, and a fold line 1714. The dilator1600 further comprises a dilatation balloon 1604, an inner dilation tube1610, a distal tip radiopaque marker 1710, and a penetrator 1302. Thepenetrator 1302 is shown extended beyond the distal end of the innerdilator tubing 1610. The penetrator 1302, which can be a separateBrockenbrough needle or an integral device, is visible on fluoroscopyand the tip can be maintained proximally to the tip radiopaque marker1710, which can be also visible under fluoroscopy, prior to advancingthe penetrator 1302 to pierce the atrial septum. The distal tipradiopaque marker 1710 can be a ring or band of tantalum, platinum,iridium, gold, or the like. The thickness of the marker 1710 can rangefrom 0.002 inches to 0.025 inches and preferably from 0.005 to 0.015inches to ensure good visibility on the fluoroscope. The distal dilatorRO marker 1710 can be affixed to the dilator tubing 1610 by processessuch as, but not limited to, adhesives, bonding, welding, overmolding,or the like. The distal dilator RO marker 1710 can be preferably affixednear the distal end of the dilator tubing 1610 and can be spaced from0.005 inches to 0.5 inches, and preferably between 0.010 and 0.25 inchesfrom the distal end of the dilator tubing 1610. When the penetrator 1302is advanced distally beyond the distal RO marker 1710, the penetratorcan be substantially exposed and capable of punching through tissue. Thedistal RO marker 1710 can be covered by a distal tip fairing, nose cone,or other sleeve. The dilator 1600 comprises the dilator hub 1320 (FIG.13), which can be affixed to the dilator shaft 1302. The dilator hub1320, in an embodiment, further comprises anti-rotation elements (notshown) to prevent it from rotating relative to the sheath hub 1406 (FIG.14). In an embodiment, such anti-rotation elements can include tabs onthe dilator hub 1320 and slots on the sheath hub 1406, or visa versa,which can disengage by simple axial retraction of the dilator hub 1320proximally away from the sheath hub 1406. The anti-rotation elements canprevent inadvertent distortion of the sheath system 1700 duringinsertion and manipulation inside the patient. The dilator 1600 canfurther comprise a fairing or distal shroud (not shown) that preventsthe distal edge of the folded sheath tubing 1404 from catching on tissueas it can be being advanced distally. This distal shroud serves as ashoehorn to ensure that the sheath 1400-dilator 1600 combination 1700can be smoothly advanced through a tissue puncture or endovascular lumenwithout becoming caught or hung up. The distal shroud can be preferablyelastomeric to expand with the dilatation balloon 1604 and can beaffixed at its distal end to the dilatation balloon 1604 or innerdilator tubing 1610, or both. The distal shroud retracts distally awayfrom the expandable distal section 1404 of the sheath 1400 because itcan be affixed to the dilator 1600.

FIG. 17B illustrates the sheath system 1700 in its radially, ordiametrically, expanded configuration. The sheath system 1700 comprisesthe dilator 1600 and the sheath 1400. Also shown in FIG. 17B are thechevron transition zone 1704, the proximal balloon anchor 1506, thedistal balloon anchor 1508, the anchor inflation line 1332, the steeringlinkage lumen 1424, and the sheath radiopaque marker 1702. Thedilatation balloon 1604 is shown in its expanded, inflated configurationover the inner dilator tubing 1610. When the dilator balloon 1604 isdeflated, the distal shroud (not shown) collapses diametrically and canbe easily pulled proximally through the expanded tubing 1404 as thedilator 1600 is being withdrawn. The distal dilator RO marker 1710 isshown affixed to the dilator inner tubing 1610. The penetrator is notvisible in this Figure and so can be retracted proximally to the distaldilator radiopaque marker 1710. By using the distal dilator RO marker1710, it is possible to remove at least one step from the procedure.Typically the length of Brockenbrough needle protrusion beyond thedistal end of the dilator can be correlated with the distance betweenthe sheath hub and the Brockenbrough needle hub. This can beaccomplished by inserting the Brockenbrough needle inside the sheath andmeasuring the distance between the dilator hub and the Brockenbroughneedle hub with the Brockenbrough needle tip just proximal to the distalend of the sheath. This measurement step can be avoided as long as thephysician is instructed not to allow the Brockenbrough needle to passdistally to the dilator distal RO marker prior to performing anypunching procedural steps.

FIG. 17C illustrates the sheath 1400 after removal of the dilator 1600(FIGS. 17A and 17B). The sheath 1400 further comprises the sheath hub1406, the lever 1420, the proximal tubing 1402, the distal tubing 1404,the proximal anchor 1506, the distal anchor 1508, the sheath radiopaquemarker 1702, and the transition zone 1704. The sheath 1400 can be fullyexpanded at its distal end 1404 and the proximal and distal anchors 1506and 1508 are deflated. The proximal tubing 1402, the distal tubing 1404,or both can be fabricated using composite construction comprising alubricious inner layer, a reinforcing layer, and an outer lubriciouslayer. Suitable materials for use in fabricating the inner layer and theouter layer include, but are not limited to, polyurethane, polyethylene,polypropylene, Hytrel, PEBAX, polyamide, and the like. Wall thicknessesof these layers can range from 0.0005 to 0.025 inches and preferablybetween 0.001 and 0.010 inches. In another embodiment, an elastomericlayer can be disposed outside the reinforcing layer and under the outerlayer. In yet another embodiment, an elastomeric layer can be disposedbetween the reinforcing layer and the inner lubricious layer. Theelastomeric layer can be fabricated from materials such as, but notlimited to, thermoplastic elastomer, silicone elastomer, polyurethaneelastomer, C-Flex, or the like. The proximal tubing 1402 in anotherembodiment, can be configured with a plurality of lumens to control themotion of multiple catheters that can be inserted therethrough. In anexemplary embodiment, the proximal tubing 1402 comprises two lumens thatcan each accept an 8 French catheter, or smaller, inserted therethrough.The lumens can be discreet or the separator wall can be removed at leastin part to minimize catheter size. In the multiple lumen embodiment ofthe proximal region, the dilator 1600 can be inserted through one of thelumens. The cross-sectional shape of the proximal tubing 1402 canfurther be configured as non-circular to minimize the cross-sectionalarea while two round catheters, such as EP ablation or diagnosticcatheters, are inserted therethrough. The distal region 1404 can besimilarly ovalized or non-round but, because of its malleable nature,the distal region 1404 can be made capable of simply deforming to acceptthe two or more catheters. The sheath hub 1406 can further be configuredwith dual hemostasis valves and further include “Y” guides to facilitateplacement of dual (or more) catheters therethrough.

FIG. 18A illustrates a cross-sectional view of the sheath proximal end1402. The proximal region 1402 further comprises the sheath tubing 1800,the outer dilator tubing 1802, the inner dilator tubing 1610, theguidewire 200, the penetrator linkage 1334, the steering linkage lumen1424, and the anchor inflation lumen 1332. The sheath tubing 1800 canbe, in an embodiment, a composite tube with an inner layer of lubriciousmaterial, an outer layer, and an intermediate reinforcing layerfabricated from a coil or braid. The coil or braid in the proximalregion 1402 possesses spring characteristics and can be fabricated fromstainless steel, titanium, nitinol, cobalt-nickel alloys, or the like.The coil or braid can also be fabricated from polymers such as PET, PEN,polyamide, HDPE, or the like. In an exemplary embodiment, thereinforcing layer can be a braid of PEN. The coil configuration can befabricated from flat wire or from round wire. The coil or braid can becoated with radiopaque materials such as gold, tantalum, platinum, orthe like, to enhance radiopacity. More than one steering linkage lumen1424 can be used to achieve push-pull action, if separated by 180degrees, or two-axis steering if separated by 90 degrees, or 120degrees, for example.

FIG. 18B illustrates a cross-sectional view of the sheath distal region1404 in its collapsed configuration. The sheath 1404 further comprisesthe distal expandable tubing 1810, the collapsed dilatation balloon1604, the anchor inflation lumen 1332, the guidewire 200, the penetrator1302, the inner dilator tube 1610, one or more longitudinal folds 1714,and the steering linkage lumen 1424. The distal expandable tubing 1810can be, in an embodiment, a composite structure with an inner layer, anouter layer, both of which are formed from polymers similar to thoseused in the proximal region 1402, and an intermediate malleablereinforcing layer, preferably fabricated from annealed metals such as,stainless steel, gold, platinum, tantalum, or the like. In an exemplaryembodiment, the malleable reinforcement comprises a coil of stainlesssteel 304, which has been substantially annealed. The stainless steelcan be formed into a flat wire with a thickness of 0.002 to 0.004 inchesand a width of 0.010 to 0.040 inches. The flat wire can be formed into acoil with a spacing substantially the same as the width of the flatwire. The stainless steel wire can be coated with a layer of gold to athickness of 100 angstroms or more.

FIG. 19 illustrates a side view of a trans-septal sheath triple-port hub1900 comprising multiple instrumentation ports 1902, 1904, and 1906. Thetriple-port hub 1900 is shown in partial breakaway so that the internallumen 1914 is visible. In the illustrated embodiment, theinstrumentation ports 1902, 1904, and 1906 are affixed to the hub 1900.The instrumentation ports 1902, 1904, and 1906 further comprisehemostasis valves 1908, 1910, and 1912, which are operably connected tothe communicating lumens of the instrumentation ports 1902, 1904, and1906, which are, in turn, operably connected to the main through lumen1914 of the hub 1900. The hemostasis valves 1908, 1910, and 1912 can beof the type, including but not limited to, ring gaskets, Tuohy-Borstvalves, duckbill valves, stopcocks, ball valves, a combination thereof,or the like. The sheath dilator 1916 is shown slidably inserted into thesheath hub 1900 through the central hemostasis valve 1910, which can bea Tuohy-Borst valve in the illustrated embodiment. The Tuohy-Borst valve1910 can be releasably tightened to restrain the position of the sheathdilator 1916 from moving in the axial direction. An advantage of thetriple port hub 1900 over a two port hub can be that it can accommodatethe dilator 1916 through the central port 1904 and a catheter eachinserted through the sideports 1902 and 1904. The central port 1904 canbe larger in diameter than the two sideports 1902 and 1906 and thecentral port 1904 can accommodate very large catheters up to 10 to 30French in diameter. The Tuohy-Borst valve 1910 can be configured topermit sealing around these large catheters and can optionally closecompletely or partially. The partial closure Tuohy-Borst valve requiresa hemostasis adapter (not shown) in order to plug the partial openingand prevent loss of hemostasis or ingress of air.

The dilator 1916 can be withdrawn from the hub 1900 following inflationof the expandable part of the sheath (not shown) and deflation of theballoon (not shown) on the dilator 1916. The dilator 1916 generallyrequires a larger port than that used for catheterization so the centralport 1904 can be configured for this task. The side ports 1902 and 1906have lumens that can accommodate catheters in the approximate range of 4to 10 French or larger in diameter.

FIG. 20A illustrates a side view of the distal end 2000 of anotherembodiment of trans-septal sheath and dilator comprising curvature nearits distal end to facilitate trans-septal puncture. In this embodiment,the distal end 2000 comprises a transition zone 2002, an expandabledistal region 2004, a distal tapered fairing 2006, a stylet 2008, and aproximal zone 2010 further comprising an outer layer 2014, anintermediate reinforcing layer 2012, and an inner layer 2016. The distalend 2000 also comprises a flexible zone 2026 further comprising an outerlayer 2018, an intermediate reinforcing layer 2022, an inner layer 2024,a plurality of vent holes 2028, and a flexible intermediate layer 2020.The tapered distal fairing 2006 further comprises at least one pressurerelief vent 2030. The tapered distal fairing 2006 and the distal mostpart of the expandable region 2004 can comprise a lubricious outercoating 2032.

Referring to FIG. 20A, the flexible zone 2026 can be disposed proximalto the expandable distal region 2004 and can be affixed thereto by thetransition zone 2002. The flexible zone 2026 can be affixed to anddisposed distal to the proximal zone 2010. The flexible zone 2026 can becharacterized by the flexible intermediate layer 2020. The flexibleintermediate layer 2020 can be comprised of elastomeric materialsincluding, but not limited to, thermoplastic elastomer, siliconeelastomer, polyurethane elastomer, polyester elastomer, or the like. Anexemplary thermoplastic elastomer can be commercially available underthe name of C-Flex. The flexible intermediate layer 2020 can have asticky or tacky surface which may be unsuitable for body or bloodcontact. For this reason, the flexible intermediate layer 2020 can bepreferably sandwiched between the inner layer 2024 and the outer layer2018, both of which can be fabricated from lubricious materials such as,but not limited to, high durometer polyurethane, polyethylene,polypropylene, polytetrafluoroethylene, polyamide, or the like. Theflexible zone 2026 can advantageously increase the flexibility of asheath, especially a large diameter sheath in selected regions. Thisincreased flexibility can be beneficial when the sheath requiressteering by a device such as a Brockenbrough needle or when a largediameter sheath with specific strength characteristics must follow aguidewire. The reinforcing layer 2022 can be embedded within theflexible intermediate layer 2020 or it can reside either inside oroutside the flexible intermediate layer 2020. The flexible intermediatelayer 2020 can reside only in the flexible region 2026 or it can extendpartially or fully across the transition zone 2002 and partially orcompletely extend to the distal end of the expandable region 2004. Inthe illustrated embodiment, the reinforcing layer 2022 can be a braidedtubular structure and can be fabricated from material such as, but notlimited to, PEN, PET, stainless steel, titanium, nitinol, or the like.The braided reinforcing layer 2022 can be suitable for torquetransmission and longitudinal pushability as well as kink resistance.This braided reinforcing layer 2022 can be the same material andstructure as that used for the proximal reinforcing layer 2012 or it canhave a different structure or material makeup.

The stylet 2008 can be a packaging aid fabricated, for example, fromspring stainless steel, titanium, or the like. The stylet 2008 can beformed straight or formed with a curve such as shown in FIG. 20A. Thecurved stylet 2008 can help maintain the distal end 2000 in a curvedconfiguration prior to use by the physician. The stylet 2008 can be acircular mandrel that can be slidably engaged within the central lumenof the sheath dilator. The diameter of the stylet 2008 can range betweenapproximately 50% and 95% of the dilator central lumen and in anembodiment, can range in size between approximately 0.035 and 0.050 fora dilator central lumen configured to accept a Brockenbrough needle. Thestylet 2008 can have a length of 1 cm to 100 cm and preferably rangebetween 5 cm and 50 cm. The vent holes 2028 perforate completely throughthe sheath wall and operably connect the inner sheath lumen to theenvironment outside the sheath. The vent holes 2028 can be used forflushing and aspiration of the sheath prior to being inserted within thepatient. The flushing can be generally performed using a syringe (notshown) filled with heparinized saline. Referring to FIG. 19, the syringecan be operably connected to one or all of the sheath sideport stopcocks1920 which are affixed to the purge lead lines 1922. The heparinizedsaline can be injected into the stopcocks 1920 and flows into thecentral lumen of the sheath 1914 where it can flow to the distal end ofthe sheath, displacing air as it moves, and exit at the vent holes 2028,which are disposed proximate the distal end of the sheath, eitherproximate the transition zone 2002 or the expandable region 2004. It canbe advantageous or important to remove air from the system prior to useso that air is not entrained into the patient's cardiovascular systemduring use, an event that could lead to ischemic sequelae. Aspirationcan also be performed through the vent holes 2028 by withdrawing avacuum on the stopcock and withdrawing blood into the vent holes 2028,again to displace air.

The pressure relief vent 2030 can be a hole or slit in the distalfairing 2006 that operably communicates with the underside of the distalfairing 2006. Fluid injected into the central lumen of the sheath canfind its way under the distal fairing 2006 and a buildup of pressureunder the distal fairing 2006 can be relieved by the pressure reliefvent 2030. The distal fairing 2006 and a portion of the expandableregion 2004 can be coated with a thin layer of hydrophilic lubriciouscoating 2032. The lubricious coating 2032 advantageously extends onlypartially or completely to approximately the transition zone 2002.Grasping the distal end of the sheath can be important during insertionand the lubricious coating 2032 should not extend to the region wherethe sheath can be grasped or the grip will be compromised. In anembodiment, the distal most 2 to 3 cm of expandable region 2004 can becoated along with the fairing tip 2006. Typical lubricious coatings 2032can be polyurethane based and can be adhered to the sheath outer surfaceby mechanical or chemical bonding. Other coatings 2032 can includeheparin or other anticoagulants or antimicrobial agents.

The transition zone 2002 can be a simple butt joint between the materialof the expandable region 2004 and the flexible region 2026. In anotherembodiment, illustrated in FIG. 20, the transition zone 2002 cancomprise chevrons 2034 or interdigitating fingers of material to providefor a gradual transition of material properties with in the transitionzone. In one embodiment, the built-up construction of the flexibleregion 2026 can be the same as that within the expandable region 2004with the exception that the reinforcing layer 2022 in the flexible zonecan be preferably elastomeric and braided, while the reinforcing layer(not shown) in the expandable region 2004 can be preferably highlymalleable. The reinforcing layer (not shown) in the expandable region2004 can be a coil of flat wire, or it can be a braid, stent-shape, orother structure. In an embodiment, only the reinforcing layer changesacross the transition zone 2002 and in this embodiment, the non-chevronconfiguration can be more appropriate. The curve shown in the distal endof the sheath 2000 can either be passive and supported by the stylet, orit can be heat-set in place during manufacturing. In the illustratedembodiment, the primary curve can be in the flexible region 2026 and itcan be desirable to use materials in the flexible region 2026 that canretain their shape once set. Such materials include, but are not limitedto polyethylene, PTFE, Hytrel, C-Flex, PEBAX, and the like.

FIG. 20B illustrates a side view of the distal end of the sheathcomprising the expandable tubing 2004 further comprising a distal end2044, the tapered distal fairing 2006, the dilator tubing 2038, a distalradiopaque marker 2034, the pressure relief port 2030, and a fairingfastener 2040 further comprising a fairing fastener to tubing bond 2042.The tapered distal fairing 2006 further comprises the reverse taper 2036at its proximal end. The reverse taper 2036 thins out the fairing nearthe proximal end so that it can flex and follow the expandable tubing2004 as it can be routed into the patient. The tapered distal fairing2006 can be shown covering the distal end 2044 of the expandable region2004. In another embodiment the tapered distal fairing 2006 can butt upagainst, but not cover, the distal end 2044 of the expandable region2004. The fairing fastener 2040 can be affixed to the dilator tubing2038 near the distal end by the bond 2042, said bond 2042 being formedby welding, melting, adhesive bonding, mechanical interlock, or thelike. The fairing fastener 2040 can be fabricated from the same orsimilar materials as the dilator tubing 2038 to ensure an optimalattachment. In an embodiment, the fairing fastener 2040 can be embeddedwithin the distal fairing 2006. In an embodiment of the manufacturingprocess to form the bond 2042, the distal fairing 2006 can be placedover the dilator tubing 2038. The fairing fastener 2040 can be placedover the dilator tubing 2038 distal to the distal fairing and can bemoved so that its proximal end extends over the outside of the distalfairing 2006. A length of shrink wrap can be placed around the fairingfastener 2040 and distal fairing 2006. Heat can be applied to the shrinkwrap which reduces in diameter and generates radially inward pressure onthe fairing fastener 2040. In combination with the heat, which melts thedistal fairing 2006, and welds the fairing fastener 2040 to the dilatortubing 2038, the force of radial compression causes the fairing fastener2040 to become embedded within the distal fairing 2006 and the distalend of the fairing fastener 2040 bonds or becomes welded to the dilatortubing 2038. In an embodiment, the distal fairing 2006 can be fabricatedfrom silicone elastomer, thermoplastic elastomer, Hytrel, or the like.In another embodiment, the distal fairing 2006 can be loaded with bariumsulfate, tantalum powder, bismuth sulfate, or the like to improveradiopacity and allow for visibility of the distal fairing 2006 underfluoroscopy or X-ray. In an embodiment, the distal fairing 2006 can beinjection molded, liquid injection molded, or cast.

A embodiment of the trans-septal sheath can be the procedure or methodof use. An exemplary procedure begins by preparing the device asfollows. A standard cardiac, trans-septal preparation should becompleted per hospital protocol. Standard fluoroscopic equipment shouldbe available for use during the procedure. Proper radiologicalprotection should be provided for all attending personnel. Using aseptictechnique, remove the sheath from its sterile pouch. Visually inspectthe sheath to make sure there is no distortion or kinking in the shaftof the sheath or in the folded distal end and that a smooth taper existsbetween the distal end of the sheath and the balloon dilator. Theballoon dilator shaft is clamped into position within the Sheath by theclosed Tuohy-Borst valve on the proximal end of the Sheath. Use aseptictechnique for all steps of the procedure. Open the three-way stopcock,located on the through-lumen flush port of the sheath, and flush withsterile, heparinized saline. Close the stopcock. Open the three-waystopcock on the sheath sideport flush port and flush with sterile,heparinized saline to ensure that all air is removed from the Sheath.Verify saline flow from the distal drain ports on the sheath. Close thestopcocks to prevent saline loss or air embolism during the procedure.Remove a Brockenbrough Needle from its package and remove the styletfrom the Needle. With the stopcock in the open position, flush theBrockenbrough needle with heparinized saline. Reinsert the stylet andlock it onto the hub. Open the three-way stopcock on the Expander FlushPort and flush with sterile, heparinized saline to ensure that all airis removed from the Expander guidewire lumen. Open the Tuohy-Borst valveon the proximal end of the Expander Hub and verify saline flow outthrough the Tuohy-Borst valve. Close the stopcock and Tuohy-Borst valve.Loosen the Tuohy-Borst valve and fully insert the Brockenbrough needleinto the Tuohy-Borst valve on the Expander. Advance the needle until itextends beyond the distal tip of the Expander. Withdraw theBrockenbrough needle until its tip is just within the distal end of theExpander. Measure the distance between the pointer flange on theproximal end of the Brockenbrough needle and the proximal end of theTuohy-Borst valve on the Expander Hub.

Fully remove the Brockenbrough needle from the sheath dilator assembly,open the 3-way stopcock, and again flush through the dilator flush port,using heparinized saline, making sure fluid flows from the distal end ofthe dilator. Attach the through lumen of a high pressure stopcock to ahigh pressure line attached to a pressure transducer for laterconnection to the Brockenbrough needle for intra-atrial blood pressuremeasurements. A Seldinger preparation and access are completed into theright femoral vein using, for example, an 18-gauge thin wall accesshollow needle. A 0.038″ stiff guidewire with a floppy tip is advancedthrough the access needle and into the femoral vein. Route the 0.038″guidewire into the venous system, through the inferior vena cava, andinto the superior vena cava under fluoroscopic guidance.

Ensure that all hemostasis valves and Tuohy-Borst valves are closed andthat all ports have been flushed and primed with heparinized saline andare free of air. The sheath with its integral balloon dilator isadvanced as a single unit, under fluoroscopic control, over the 0.038″guidewire until its tip radiopaque marker is positioned well within thesuperior vena cava. Inject radiopaque contrast media through the dilatorflush port, as required, under fluoroscopic visualization to ensurecorrect placement. Carefully controlling the hemostasis valve at theproximal end of the dilator hub, remove the guidewire. Carefully attacha 10-cc syringe filled with 1-cc of sterile heparinized saline to thedilator flush port and withdraw until blood is observed. Repeat thisprocedure to ensure the dilator flush port is free of air. Insert theBrockenbrough needle with stylet into the needle guidewire port of thedilator and route the Brockenbrough needle so that its tip is alignedbehind (proximal to) the radiopaque marker located at the distal tip ofthe sheath dilator. This is confirmed using the dimensions measuredearlier between the pointer flange and the sheath proximal end. Rotatethe Brockenbrough needle and sheath dilator so that the pointer on theBrockenbrough is aligned with the sheath hub sideport and that bothBrockenbrough pointer and sheath hub Sideport are oriented medially.Remove the stylet from the Brockenbrough needle and attach the 3-way,high pressure stopcock with attached pressure transducer to the Luerport of the Brockenbrough needle. Attach a 10-cc syringe filled with1-cc of heparinized, sterile saline to the side port of the 3-waystopcock. Withdraw blood into the 10-cc syringe. Close the 3-waystopcock and remove and discard the syringe. Repeat the blood withdrawalwith another new 10 cc filled with 1 cc of heparin to ensure the absenceof air.

The sheath dilator assembly, with Brockenbrough needle inserted, iswithdrawn caudally with the tip of the Brockenbrough needle orientedmedially, toward the atrial septum as evidence by the orientation of thepointer flange being at 3:00 to 5:00 as observed from the patient'sfeet. Withdrawal of the sheath dilator assembly will result in the tipmoving medially when it enters the right atrium. When, upon furtherwithdrawal, the tip of the sheath dilator assembly abruptly movesmarkedly medially into the fossa ovalis, further withdrawal isdiscontinued and the atrial septal wall should be engaged. The fossaovalis is now “tented” toward the left atrium. Using a 10-cc syringefilled with radiopaque contrast media, inject a small amount of contrastmedia through the high pressure stopcock attached to the central lumenof the Brockenbrough needle to “paint” the fossa ovalis with a mark thatis visible under fluoroscopy. Carefully monitoring the pressure withinthe lumen of the Brockenbrough needle, the Brockenbrough needle is nextadvanced out of the sheath dilator assembly and through the atrialseptum into the left atrium, taking care not to move the sheath dilatorassembly. Continuous fluoroscopic monitoring is essential during thisphase. The fossa ovalis will, under mechanical pressure, move laterallyover the sheath dilator assembly so that the distal end of the sheathdilator assembly now resides within the left atrium as indicated bypressure waveforms consistent with the left atrium and fluoroscopicobservation. The proximal and distal sheath radiopaque markers (secondand third RO markers from the distal end of the sheath dilator assembly)should now straddle the position of the fossa ovalis the location ofwhich is evidenced by the “painted” mark generated in a prior step.

A dilute 50% solution of radiopaque contrast media, and sterile salineis prepared and approximately 25-CC are drawn up into a high-pressureballoon inflation syringe equipped with a pressure gauge. Care should betaken to remove all air from the syringe, the dilator, and associatedtubing. Attach the pressure line of the inflation device to the throughlumen of the 3-way stopcock attached to the dilator balloon inflationport. Attach a syringe, filled with radiopaque contrast media, to theother lumen of the three-way stopcock. Under fluoroscopic control, thedilute contrast media is injected up to the maximum rated inflationpressure. It is normal to observe a drop in pressure as the dilatorballoon progressively expands the folded distal section of the sheath.The rated inflation pressure should be maintained for a minimum of 30seconds to expand any “waist” that may remain along the length of theexpanded sheath.

Apply suction, using the high-pressure syringe, to theinflation/deflation port attached to the 3-way stopcock on the balloondilator hub in order to deflate the balloon of the dilator. Slightlyloosen the Tuohy-Borst valve on the through lumen at the proximal end ofthe sheath hub. Remove the deflated dilator from the expanded sheathbeing careful to immediately close the Tuohy-Borst valve to preventblood loss. Introduce the appropriate therapeutic or diagnostic catheterthrough the central working channel of the expanded sheath into the leftatrium. A 9 French hemostasis adaptor (provided) may be inserted andsealed within the Tuohy-Borst valve to facilitate introduction andremoval of diagnostic or therapeutic devices. This adaptor may be placedafter the dilator has been removed from the Tuohy-Borst valve. Beforeplacement, flush the adaptor with heparinized saline to remove air.Insert the stem of the hemostasis adaptor into the Tuohy-Borst valve andtighten snugly by hand. When the hemostasis adaptor is secured, connecta 10 cc syringe filled with 1 cc of heparin to the adaptor sidearmstopcock and withdraw blood to ensure the absence of air in the system.The hemostasis adapter is now ready for use. Remove any instrumentationfrom the sheath, being careful to control the Tuohy-Borst or hemostasisvalves to prevent blood loss. While maintaining hemostasis and usingstandard hospital procedure to control a venous percutaneous puncturesite, gently withdraw and remove the expanded sheath from the venouscirculation when the procedure has been completed.

FIG. 21A illustrates a side view of a hemostasis adapter 2100 comprisingan adapter hub 2102, a length of adapter tubing 2104, a hemostasis valve2106, a sideport 2114 further comprising a purge line 2108 and astopcock 2110, and a tubing enlargement 2112. The tubing enlargement2112 can be a cylindrical or radially enlarged structure, bonded,welded, or mechanically affixed to the adapter tubing 2104. The hub 2102can be affixed to the proximal end of the adapter tubing 2104. Theadapter tubing 2104 comprises a central through lumen 2116 extendingfrom the proximal end to the distal end of the adapter tubing 2104. Thesideport 2114 can be affixed to the hub 2102 and operably connected tothe central through lumen 2116. The purge line 2108 can be affixed tothe sideport 2114 at one end and to the stopcock 2110 at the other end.The hemostasis valve 2106 can be a ring orifice, duckbill valve, flapvalve, or a combination thereof. In a preferred embodiment, thehemostasis valve 2106 comprises a proximal ring seal and a distal flapvalve to optimize the valving function. The enlargement 2112 can beconfigured to serve as a tactile stop or detent so that an operator canfeel how far to insert the hemostasis adapter tubing 2104 into a hub ofanother sheath (not shown). The enlargement 2112 can be advantageouslybeveled or tapered at one or both ends to facilitate passage throughlarger valves or ports. The adapter tubing 2116 can also be beveled atits distal end to facilitate passage through another tube or valve (notshown).

FIG. 21B illustrates the hemostasis adapter 2100 inserted through theTuohy-Borst valve 1910 on the central through port of a sheath hub 1900.The sheath hub 1900 comprises a large diameter Tuohy-Borst valve 1910,which can have a capacity ranging from 10 to 30 French. Such largeTuohy-Borst valves 1910 may not seal fully on closure, or it may seal atall unless it surrounds a tube larger than 5 or 6 French, for example.The hemostasis adapter 2100 can be inserted into such a Tuohy-Borstvalve 1910 and the Tuohy-Borst valve 1910 tightened to obtain a sealaround the hemostasis adapter tubing 2104, which can range in diameterfrom 5 to 10 French. In an embodiment, the Tuohy-Borst valve 1910 canseal around and allow passage of tubing ranging from 6 to 18 French indiameter. The enlargement 2112 can pass through the Tuohy-Borst or othervalve 1910 but with increased force, which can be relieved once theenlargement 2112 can be past the valve 1910. The enlargement 2112 alsohelps prevent inadvertent withdrawal of the hemostasis adapter 2100 fromthe sheath hub 1900. The stopcock 2110 and purge line 2108 can be usedfor aspiration of blood or saline or purging of air from the adapterlumen 2116 or the sheath lumen 1914.

FIG. 22A illustrates a side view of the distal end 2200 of an expandabletrans-septal sheath with the dilator removed. The distal end 2200 can beshown in partial breakaway view so the reinforcing structures 2208 and2210 can be visualized. The distal end 2200 comprises a proximalreinforcement 2208, a sheath distal tubing wall 2204, a central sheathlumen 2214, a distal reinforcement 2210, a distal radiopaque marker2212, and a transition zone 2206. In an embodiment, the distalreinforcement 2210 can be a flat wire fabricated from annealed stainlesssteel. In another embodiment, the distal reinforcement can be a flatwire fabricated from annealed stainless steel that has been coated witha radiopaque coating such as, but not limited to, gold, platinum,iridium, tantalum, or the like. The coating can be in the range of 50 to300 angstroms to maximize visibility under fluoroscopy. Theradiopacity-enhanced distal reinforcement 2210, in the illustratedembodiment can be in the shape of a coil but could be another structurelike a zigzag shape. The distal radiopaque marker 2212 delineates thedistal end of the sheath tubing 2200. In the illustrated embodiment, theproximal reinforcement 2208 can be a braided structure fabricated fromspring wire or elastomeric polymer. The proximal end of the transitionzone 2206 can be where the proximal reinforcement 2208 ends. The distalreinforcement 2210 can be affixed to the sheath wall 2204 by firstplacing an inner polymer layer, fabricated from polyethylene forexample, over a mandrel, followed by the reinforcing coil 2210. An outerlayer can be then placed over the reinforcing coil 2210 and the entirestructure can be heated under pressure by using shrink wrap, for examplePET or PTFE, to provide radially directed inward force to fuse thestructure given the applied heat.

FIG. 22B illustrates a side view of the distal end 2220 of an expandabletrans-septal sheath with the dilator removed. The distal 2200 end of thesheath is shown in partial breakaway view so that the reinforcement canbe visualized. The distal end 2200 comprises the transition zone 2206,the sheath wall 2204, the distal reinforcement 2210, the distalradiopaque marker 2212, and a parallel wound coil of radiopaque wire2222. The transition zone 2206 can comprise a chevron shape withinterdigitating fingers, as illustrated, or it can be a simple flat buttjoint. The parallel wound coil 2222 can be preferably fabricated fromgold, platinum, tantalum, iridium, or the like. The parallel wound coil2222 and the distal reinforcement 2210 are affixed to the sheath wall2204 by first placing an inner layer over a mandrel, followed by thereinforcing coil 2210 and the parallel wound coil 2222. An outer layercan be then placed over the coils and the entire structure can be heatedunder pressure by using shrink wrap to provide radially directed inwardforce to fuse the structure.

By varying the length of the expandable region, different properties canbe achieved. A short expandable region allows for a stiffer catheterwith highly controllable characteristics, wherein curves can be heat setinto the structure more readily. A longer expandable region allows thesheath dilator system to be bent and articulated by a guidewire orBrockenbrough needle, inserted through the central lumen of the dilator.In an embodiment, the expandable region can be approximately 10 to 30 cmlong and preferably between 15 and 25 cm long. In another embodiment,the expandable region can be between 1 and 10 cm long and preferablybetween 2 and 5 cm long. In the embodiment where the expandable lengthcan be short, an enhanced flexible region can be used as part of thecatheter to improve flexibility, even when the sheath can be a largediameter structure. In either embodiment, it can be beneficial that theBrockenbrough needle be able to steer the sheath dilator system to pointtoward the fossa ovalis.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. For example, thesheath may include instruments affixed integrally to the interiorcentral lumen of the sheath, rather than being separately inserted, forperforming therapeutic or diagnostic functions. The hub may comprise tiedowns or configuration changes to permit attaching the hub to the mouth,nose, or face of the patient. The dilatation means may be a balloondilator as described in detail herein, it may rely on axial compressionof a braid to expand its diameter, or it may be a translation dilatorwherein an inner tube is advanced longitudinally to expand anelastomeric small diameter tube. Dilation may also occur as a result ofunfurling a thin-film wrapped tube or by rotation of a series of hoopsso that their alignment is at right angles to the long axis of thesheath. The embodiments described herein further are suitable forfabricating very small diameter catheters, microcatheters, or sheathssuitable for cardiovascular or neurovascular access. Various valveconfigurations and radiopaque marker configurations are appropriate foruse in this device. The described embodiments are to be considered inall respects only as illustrative and not restrictive. The scope of theinvention is therefore indicated by the appended claims rather than theforegoing description. All changes that come within the meaning andrange of equivalency of the claims are to be embraced within theirscope.

1. An expandable endovascular access sheath adapted for providingminimally invasive access to the left atrium, comprising: an axiallyelongate sheath tube with a proximal end, a distal end, and a centralthrough lumen; a distal region of the sheath which is expandable incircumference in response to outward pressure applied therein, thedistal region of the sheath comprising at least one diametricallyexpandable region that comprises a malleable reinforcement structure inwhich the at least one diametrically expandable region is longitudinallyfolded into a reduced cross-sectional profile and can be expanded to asecond cross-sectional configuration in which the at least onediametrically expanded region is unfolded into a larger cross-sectionalprofile; a hub affixed to the proximal end of the sheath tube, the hubadapted to facilitate the passage of instrumentation, the hub comprisinga valve; a central obturator, which serves to occlude the central lumenof the sheath during insertion further comprising a hub that releasablylocks to the hub of the sheath; and a guidewire lumen within theobturator, capable of passing over standard medical guidewires and whichwill allow the obturator and sheath to track over said guidewiresthrough tortuosity such as that found tracking into the right and leftatria, and any transitions therebetween; wherein the obturator is aballoon dilator capable of expanding the distal region of the sheathfrom a collapsed configuration to an expanded configuration; ahemostasis adapter comprising an adapter hub and a adapter tubingconfigured to be inserted into the valve of the hub on the proximal endof the sheath tube, the adapter tubing including an enlargementconfigured to pass through the valve of the hub.
 2. The endovascularaccess sheath of claim 1 wherein the sheath tube comprises: an outerlayer, an inner layer, and the reinforcement structure wherein the outerlayer and the inner layer are fabricated from polymeric materials. 3.The endovascular access sheath of claim 2 wherein the reinforcementstructure is a coil of metal.
 4. The endovascular access sheath of claim2 wherein the reinforcement structure is a braid.
 5. The endovascularaccess sheath of claim 2 wherein the inner and outer layer arefabricated from different polymeric matrerials.
 6. The endovascularaccess sheath of claim 2 wherein the length of the sheath is between 50and 250 cm.
 7. The endovascular access sheath of claim 2 wherein thecentral through lumen of the sheath ranges between 6 and 30 French whenthe distal region is fully expanded.
 8. The endovascular access sheathof claim 1 where the sheath tube comprises the reinforcement structureembedded within a membrane layer fabricated from polymeric materials.